Ok, got the vert back from the shop, after 2 months (they said 2 weeks...ha!) and pulled the numbers tonight. Supposedly this is a 383 with a roller cam.

Block is 3970010 with a date code of...heck, can't find my note now. Heads are 3947041, with L 7 8 and K 15 8. Should this be a 350 from 1969?

Odd part - The roller rockers have both 1.5's and 1.65's running on the valves, is that normal? I thought they were always the same size.

-shoe

3970010 is a 350 block, not sure of what year though. It is somewhat common to have a different ratio rocker arm on the exhaust valve than on the intake valve. But all exhaust valve rockers should be the same ratio and all intake valve rockers should be the same.(but intake can be a different ratio than exhaust) Hope that makes some sense.

3970010 is a 4" bore small block. My 302 is a 3970010.

To add to the info, 041 heads are small chamber, higher compression heads. If you put them with flat top pistons on a 383, compression is in the 11s at least. The way you check for a 383 is to look at the harmonic balancer. If it is flat all the way around, its not a 383, if it has a flat and scooped edge, then it probably is. only caveat to this is if they use an internally balanced crank (more $$ and most people dont).

Does the engine run like 11:1 compression?

Don't completely understand the flat all the way around part, but believe you mean it is "squared" on all sides? The balancer is flat only in the front. The round outer surface has a raised edge about 3/8" in the front (all the way around). The back of the balancer on the crank is completely concave beyond the first inch or so of "flat" area. (ok, I read this twice and can't figure out what I said either).

It isn't running right now, just misfires at any timing range and when you think you have it right, it pops out the carb like a broken exhaust spring any time you hit the gas. Oh well, at least it is at home now so I can start messing with it when I have spare time, whatever that is.

-shoe

If your 383 is externally balanced it'll use a Balancer and flexplate-flywhhel from a 400SBC,,,,, if its internally balamced the balancer and flexplate will be from a 350.
Still confused?
Go to the parts store and ask to see each of those 4 items.