All three stores (Autozone, Napa and Lee Auto Parts) in my town don't carry these. Are they interchangeable with some older vehicle?

 

Try any tranny shops?

 

I don't even think we have any tranny shops in this town.
Napa carries shims for a 305 M5 thirdgen. I'll have to check the ID/OD to see if it matches.
Thanks.

 

It should match up no problem. Anything meant for a SBC will work

 

I thought so too, but looks like they're different after all.

Center of the shim to outer holes on a '80 305/350 is 1.73" while on all 3rdgen 305s, it's 1.482".

I guess I'll just take the flywheel in and match it up with one of these.

 

That is Probadly due to crank weight. A 305 crank is lighter then a 350. From what i have read a STOCK lt1 crank is closer in weight to a 305 crank.

Hope that helps.