First timer question

Hello,

I just purchased a 1966 Skylark and the person that I got it from knew nothing about the engine. He said that he had a friend that was working on it (not in a good way) and when I got it she was not running. The past owner has had it for about 20 years and he was working on the body (removing paint). According to him it is a '71 455. I am not too sure. If anyone can enlighten me on determining what engine I have that would be very helpfull.

Where is the block casting number?

I have pulled a few numbers off of the heads and intake.
Pass Head MP1241860
Driver Head MP1241860
Intake B1245061-3

It has an HEI distributer and a 4bbl carb.

Thanks,

Superman