I have a old 350 block that I was going do a 383 build up on. I ended up getting a deal on a 454 and scrapped the 383 plans. Since I have this extra block around, can I use it in the vette with the stock L98 heads?

No, the heads are not interchangeable. Also, putting a big block in a C4 is a real chore as the intake and just about every accessory will need to be re-engineered and often requires a lot of fabrication.

Not to hijack this thread or anything but will gen 1 sbcs work in the c4s, or any sbc before the ls1?

If I read this correctly, you want to put a generation 1 small block in an 86 Vette. Should be no trouble EXCEPT the dip stick will be on the wrong side. Heads will bolt right up. The only problem would be if it's a one piece rear main seal in the 86. that would require a different flywheel. Also, you have to plug the fuel pump hole. Same for all L98's, the LT1 is different.

Sorry - I totally misread your post. Thought you wanted to toss the 454 in there. An early small block in your '86 is totally doable. The L98 heads will go on the earlier block just fine, and the hurdles you'll have to overcome are pretty small. If you're exchanging your original '86 motor, all the accessories, etc. should transfer over just fine.

No prob, wasn't there a guy on hear awhile back that did a 454 in a vette? frankenvette or something like that? Sounds good, just was not sure how the heads would work. Even thou it's an 86 I wouldn't want to do anythinhg to the stock block for later on. Look like I got me a winter project.

All SBCs are Gen I, right up until the LTx, Gen II engines, started in 1992. The LSx engines start the Gen III series in the C5s.

zr1fred hit the nail on the head. The one piece rear main seal began in 1986. The 1968 block will take a two piece rear main seal and a two piece rear main seal crankshaft and flywheel or flex plate. The opposite side dipstick will be the only other difference to deal with. ALL the accessories will fit. One year later and you would have had roller cam details to deal with.

RACE ON!!!

Just so you know if you use a 2 piece rear seal you will need to change to a different oil pan

Did all '86s have one piece rear main seals? Or was it only those fitted with alloy heads?

All

The seal change came at the model year change, and it was a GM corporate thing, not just the Corvette.

RACE ON!!!

So I would just need to get a new oil pan, not a bad swap out. Just to ask while i'm thinking about it, i'm looking to go faster. I was thinking a 480 lift cam, with my mini ram from TPIS. Since i'll have the engine out might as well do it right. Looking for daily drivability, not crazy fast but fast enough to keep up with the newer guys.

A 480 lift cam is pretty close to what I think came in the 64 327.
Still a good streetable cam