Here's my plan. After I sell off all my 400sbc stuff I want to do a cammed 5.3 with a carb and some spray(125-200), I want to use my th350 and 3500 rpm stall along with my existing 750cfm carb. I would Like to use stock 5.3 heads, but wouldn't mind having minor work done to them. I understand I will need an f body oil pan and drive accessory's. My main concern is fuel pump and wiring. I would also need help picking the cam to match my other components and matching that to a new gear ratio. My et goal is 10.7, help me make it happen.

If I were you, shooting for 10's; I would start with a 6.0 block instead of a 5.3. They can be had for not a whole lot more than the 5.3's.

10.7 is an easily attainable goal with a cam, worked heads, and n2o using a 5-3. assuming you can get the car off the line and it's not a pig, of course, you only need like 123-124mph. only having a 3500 stall is going to really limit your cam choice.

what gear ratio?
raceweight?

i can see something in the mid/high 230s duration suiting you just fine, as that would pretty much be at the limit of a 5-3 and 410 (for exmaple) gears.

I would also go with a 6.0 instead of a 5.3

I personally would also keep it EFI which will help with the tuning of the car better than with a carb, and will end up cheaper since the kits to swap over is around 500-600 bucks not including the carb, you would only need either a LS1 or LS6 intake to run on it.

Plenty of guys running 10's with LS1's

fuel pump and wiring....use the fuel system already in place. Wiring is connecting 9 connectors off a msd box. REALLY simple to hook up. Biggest cam would be a 224 or 230 duration in that small of a motor. Just fired mine up the other day, I didn't see any point in EFI with expensive tunes since I already have a big HP carb fuel system and a wideband.

Local guy here running mid 9's with LS1, LS6 heads, LS7 cam and a D1SC going through a Turbo 400 running EFI, tunes aren't that expensive and after getting it tuned you never have to change anything much afterwards.

I've always thought that swapping to a carb limits what you can do with these motors by keeping them EFI.

this thread helped me out alot with a with a question i was gonna ask.. everyone from the old classic car crowd in my family is trying to talk me into carbing my Lt1 i recenlty picked up before swap it seems the general opinion is to keep them efi.. Me i am more comp then tuner so pluggin a laptop in for the tune would be easier for me anyhow.. i am about to sell a bike i own and was thinking of using the money for manifold and carb now will just keep the cash for engine suspension mods and some of the body work i need.. thanks all for the keep it efi opinions..

just curious why you'd say this. a 5.3 is only 25 cubes (roughly) smaller than an ls1. guys are commonly running mid-high 240* duration cams in those engines (stock shortblock). i can't see knocking off 20* in duration just because it is a slightly smaller engine.

does anyone know the largest cam that will fit a 5.3 without flycutting? flat top and dish piston both if available..

sure if you want to run a bigger cam then plan on a 5500 stall and shifting it around 7k. Guys that run a high 240 duration, i'm assuming you mean a Trex cam, typically have a 4600 or bigger stall and 4.30s/4.56s. Now put this package in a motor with less compression and less cubes and what you have is a dog of a motor.

there are MANY cams out there in the mid-high 240* duration aside from the t-rex. it's all in the setup. you're absolutely right that his car would be a dog should he use a 5.3 engine and employ a t-rex cam with little to no support from the drivetrain. but i didn't suggest he use a t-rex cam. i refuse to believe that a 224 cam is the biggest he can go with a 5.3 and get down the drag strip. call me crazy, but a cam with 0* overlap isn't big. and it's definately not the upper limit on a 323ish cid dragstrip-inspired engine.

i do agree that he should go no larger than a 224 cam should he keep the 3500 stall. small cube motors need to rev to make power, as i stated before - the stall is going to really limit the OP's cam choices.

im going carb in my ls 3rd gen swap.
build is
11.2 SCR 375ci, 6.0 block
243 heads milled
TR TRex
Edelbrock Super Victor intake manifold with Holley 750 HP.
self made 1 3/4 lt headrs
full built th350, 4k stall, 3.37 gear dana rear
shooting for 575bhp on motor, also gonna go with ZEX permiter plate for 150 hit.

Say I sprung for a ls1, or Lq4, same plan as keeping it carb, what more options would I have with cam choice with the 3500 stall? Could I set my et goal lower? car is a low optioned firebird. NO a/c, heat, under padding, spare, jack. power locks. radio or speakers.

only thing left are power steering(couldn't find a s10 box) and power windows. full interior, minus headliner.

any removal of unsprung weight will help to move car quicker, and less parasitic drag on the motor will also help, running s10 will def. free up some hp along with a udp. 3500 stall is not the main thing holding u back,
its more of scr and dcr. what is your goal?
set a realistic goal with the parts u can get. also the lq4 is 9.38 scr. a .040 mill bring to 10:1 with stock gaskets. 6.0 with milled heads, ls6 intake free flow exhaust, and ls6 cam, udp will make around 420bhp range.
perhaps more if not using ps pump, im not