BB 402 questions

[JQ-72]

I have a 402 out of a '72 3/4 ton Cheyenne. I ran the #'s on the front of the block in the "Chevy red book" (TKX) and it checked out. I have the motor on an engine stand and noticed "pass. high per." on the back of the block. Also, "pass." is stamped on the top side of each head. Were there any differences in intake manifolds? When I bought the truck, the motor had a '69 Chevelle 396/350 factory high rise manifold on it. The guy I bought it from threw in a '71 BB intake manifold. I put the '71 manifold on and it did not cover up the water ports in the middle of the heads but all the bolt holes line up. Last, what is the best way to get old crusty auto paint off a motor while leaving it assembled? Thanks for any help.
Joshua