Engine ID

[blown]

c6me is a 66 390 or 428 those are the only 2 that used that block # the way to tell is lift it and look at the flywheel it will have balancing weights if its a 428 if not its just a 390 both are excellent motors.also the heads will have a 4 bolt pattern on the exhaust ports if its a 428 cj

[FWB]

use a stick, a thin one to measure the stroke through the spark plug hole.

3.78 = 390
3.98= 428 or 410, with a 65 casting date probably not a 410