I am looking for a 305, 5 speed IROC. I am planning to put build a tricked out TPI 350 for it and adding either a richmond or temec manual trans. I am graduating in May and I will finally have some $$$ to buy and trick out another car. My questions regarding the potential swap are:

1. Are the ECMs for the 305 and 350 different, or is it just the PROM?
2. For the easiest fit possible, if I wanted a brand new short block (aluminum maybe!) are their companies that sell complete 350 blocks for 88 and later f-bodies? If so, who are they?
3. Are all 350 blocks the same, whether it comes out of a 69 camaro or an 89 camaro, or where changes made along the way that will narrow my search if I opt to go with a used block?

Sorry if these ?s have been answered elsewhere, but I am just looking for some concrete info. Thanks!

 

I believe the proms are different for 305/350 cars. There are tons of places that should be able to get you a shortblock. Check your local yellow pages first, ask around to see if there are any good performance/machine shops that can build one. You can also get one mail-order or through GM. Most of the major places will ship a motor to you if you want. There are 2 flavours of short blocks you will most likely be looking at. 85 and older blocks, and 86 and newer blocks. The 86 and newer blocks use a slightly different crank (1 piece rear main seal), plus have provisions for roller cams. The 86 and newer ones are less common, and probably cost a bit more to get, but it is what I would be looking for. The ability to use a roller cam is the main reason why. The 92-97 LT1 motor uses a different engine block, and probably should be avoided, in my opinion, based upon what you are looking to do.

 

The ECM is the same, you just need the Prom.

87-95 2bolt main 1piece rear main seal blocks are what you would need for a 87 and up TPI setup.

 

Year I knew the switch to 1 piece rear main seals was done sometime in the mid 80s, but I couldn't remember what year exactly.

Do you think it would be worth the extra cost to go with 4 bolt, as opposed to 2-bolt, mains?

Thanks!

 

unless your planning on having over 450hp, then no it doesnt really matter.

 

Don't say "tricked out"

Just don't...

 

The rear main seal has nothing to do with how the intake setup bolts up to the cylinder heads. The only thing that pertains to the rear main seal is the transmission.