I got a 355 with the 1966 Chevy II me and my friend bought. Guy said it was a 383. Its not, he probably got told it was a 383 when he got it. Took the pan off. Looks like its balanced , grinding on the crank. Its got a cast crank, TRW pistons with all the knurling on them L2304. 10.6-1 w 64 cc heads. its got 76 cc 882 castings. Don't know what valves. It has Lunati 00012 cam, a hydraulic bracket master cam. .515 lift 300 dur adv, 2500-6500.. A gear drive also. I am thinking about ditching the gear drive. THe compression ratio is likely around 9.7 to 1. Is it too much cam? I have a set of 492 64cc heads with 2.02 valves. Should I swap them? With that much over lap 10.6 would likely work with premium pump gas. It has a Holley 600cfm, that has to go also. Motor looks new inside. Or should I just run it? Guy said it ran low 13's in the Nova with street tires.

I will be running a 4 speed and 3.73 gears.

Measure the stroke to see if its 3.75 inches. Rotating assembly could be a 400 CID, check for a weight on the flywheel/flexplate and a non-sysmetrical backside of the harmonic balancer.

If all smooth, then check counterweights for Mallory metal slugs for internal balance.

Head swap and timing chain read good.

Get the casting number off of the crank - there's only one for 400's (3951529) and if it's an old school 383, it'll have a 400 crank with turned down main journals.

Look for the internal/external balance. That will tell you if it is a 400 or 350 crank. Of course measuring the stroke is tell tale.

The crank is 3932442 I believe. The balancer looks normal. It looks like the crank is ground on, balanced internally. The pistons are L2304, I could see the number through the spark plug hole.

It is a 350 crankshaft.
3932442..267,305,350..cast...medium journal...3.48" stroke