[johnsma22]

You must have edited your post with the head casting numbers as I was typing my last post.

The # 62 heads were used in 1968 on Pontiac Big cars and Grand Prixs with 400's and 428's with 10.5:1-10.75:1 CR respectively.

The #62 heads were used in 1969 in all cars with 400's and 428's, depending on the combo's. Other head castings were used in those years of course. The factory lists the combustion chamber size at 72-75 cc's for 1968 depending on whether in came on a 400 or a 428. In 1969 the factory lists the chamber size as 72cc's, which yielded a CR of 10.5:1-10.75:1. We all know how inaccurate these factory numbers can be so your best bet if you intend to use them is to have a reputable machine shop cc them for you. No telling what kind of work has been done to them over the years.

These heads are considered to be high performance heads with large valves (2.11" intake/1.77" exhaust) closed chambers and screw in rocker studs.

IMO, these heads may put you into the position of not being able to run this motor on pump gas, due to the risk of detonation with such a high CR. You must find out if the block has been bored, zero decked, heads milled and so forth. That is a debate for another day I suspect. Hope this helps

John