I am about to start my swap, and the goal is to have the car driving again by May 1st. Here is what I am planning so far. How does this sound? Engine 2004 5.3 LM7 with stock 706 heads LS6 cam and yellow springs (02-04) with 7.425 pushrods LS6 intake LS6 valley cover Stock fuel injectors Fbody accessories with UD pulley and no AC Fbody oil pan Everything else Stock rebuilt 4L60e Stall for daily driver? Stock K member Hawks engine and trans swap mounts with poly bushings 00+ fbody exhaust manifolds - can these be ported? Custom y pipe and 3” back 10 bolt? Current 2.73, maybe 3.23 or 3.42? Stock TPI fuel pump? The car is going to be a daily driver and probably won’t see the track.

sounds a lot like the swap I'm working towards in the same amount of time (hopefully). I think the 10-bolt may be a bit of the weak point here, but will handle as a DD for some time while you're saving up for things. Any idea what you're doing for wiring? I know I was told to stay away from the 98 year, since its a bit different than those after. May want to up the fuel pump, but I'll leave that to someone else.

make sure to get some sfc's, you're gonna need it. make sure to keep everyone updated, we all love pics of 3rd gens with LSx motors

Same car as my swap I am swapping in a '99 LS1 with a cam and ported heads, I hoped to have it done quickly but I've been on the project since February XD

I am using '02 SS Manifolds, and the stock 10 bolt w/ 2.73's for now lol. I also just scored a brand new from GM 4L60E for 600 bucks Canadian

You're gonna want to upgrade the fuel pump. Everything else sounds good though.

I think u are probably want sumthin like 1600-1800 stall if daily driver with 3.23. Good mpg and engine should make power pretty quick.

Yeah I used a Walbro GSS340 fuel pump, was only like $99 bucks at Summit and is rated for like 500 HP or something. I also used poly mounts. I had major fitment issues with the Spohn mounts and poly inserts but that seems to be a problem limited to me only for whatever reason.

5.3 is a good DD engine but not LS6 intake stuff. It wont take full advantage of it to be worth the money. Buy the cheapo LS1 intakes

For a DD, Id stick to the stock stall. If you absolutely have to upgrade, LSx doesnt respond well unless you go big. Say 3000 or better

Fuel pump needs a boost, TPI is designed around 45psi. LS1 is 58psi constant and will wear it out quickly

Porting manifolds is a waste of time and carbide bits. If you want more power, get headers

Your MPG will like the 2.73's. Your tires will like a posi more than open diff. Dropping the gearing will make it alot faster than any other mod but your MPG will hate it

yeah i think a stock stall would prob be best...i wasn't thinking too much of what i said before. I would definatally prefer a little higher gearing if i were u. its really ur call dude! well good luck and hopefully u get it done by ur deadline!!!

I'm hoping for just over 300whp, I have read that the 10 bolt might handle this, I will try it out at least. Probably a good idea to wait on gears if the rear might go anyways. There doesn’t seem to be much difference in 3.23 vs. 3.42 so either one would work for me.

Is there anything I can do to make the fuel pump last longer? For all I know, it might be original. If the pump goes, that's when I would upgrade the rear. If I used an LS1 fuel tank and stock LS1 pump, would I be ok?

I have all of the connectors and wiring diagrams so I am going to try and make my harness myself. I know it will take me several weekends, but it can be done indoors so that’s a plus in the winter. Is there any reason besides for looks to put the PCM inside the car?

I saw that in your thread, hopefully there is a simple solution. I already have the engine and trans mount adapters, and the engine clamshells with poly inserts. For the trans mount, would I just order a poly mount for a 98+ fbody?

[quote]5.3 is a good DD engine but not LS6 intake stuff. It wont take full advantage of it to be worth the money.[quote]
Are you talking about the intake manifold? Truck guys seem to have good results with the LS6 cam, but I think most of them are still using the truck intake. The LS6 valley cover/PCV seems to fix oil issues, but I don’t know if I need to worry about that with a basically stock engine.

Stock converter, or aftermarket with the same stall speed? If anyone even makes that.

A waste of time as in little to no gain, or not close to headers? I ask only because GTP guys seem to pick up small gains (my other car is a GTP). If I could get even 5-10 hp by porting them I would try it. But I haven't read about anyone porting the LS1 manifolds, probably because they just get headers like you said.

Sorry for the long post, and thanks for the replies so far. My car is eagerly awaiting the transplant in the garage.

300 through an auto shouldnt kill the 10 bolt unless you drive like a retard

The fuel pump isnt meant to run at the higher PSI. Im not sure how else to tell you. Easy solution is the pump from a LS1 car in your stock tank. Forget the LS1 tank, thats alot of extra problems

The LS1 PCM was designed to be heat resistant and waterproof. Thus 4th gens mounted it in the engine bay. Most people move it under the dash because there really isnt a good place to put it in the 3rd gen. Plus it looks terrible

You should be fine on the mounts. Do a search on poly trans mounts. Youll see most people still run the rubber trans mount because poly isnt so nice

I was talking about the LS6 plastic intake manifold

LSx manifolds regardless of what vehicle they came from are essentially cast iron shorty headers designed for the specific engine they were equipped on. If you upgrade, go longtubes or go home

Have fun wiring. PM me if you have a question or get stuck. I wrote 3 wiring threads to take 99% of the common problems out of the job

I agree with everything Pocket just said.


I found it easiest just to put a good fuel pump in my stock tank (Walbro 255). Then I made my own fuel lines, using the part numbers from Pocket's diagram that you can find with a search.

Stock manifolds are basically shorties. If you are going to upgrade get the Hawks/SSW longtubes.

I wanted my PCM inside the car because I think that it looks pretty tacky with it mounted under the hood when you spend all this money on such a cool swap and then ruin it with all the brains laying on top of one of the fenders.


Your stock rear end will be fine...for a while. I can't say the same about mine though. I have a stock LS1 rear end with 3.42's and will be running a 6spd behind an approx. 450hp motor..... Yea, I'm saving up for a 12 bolt and trying to suck up to my wife enough to let me buy one.