[vtxman]

Your combination with 8:5 - 9:0 CR will work, it just may not reach its full potential.

After 1970, the factory lowered the compression for emission reasons etc. It's just that the Ram Air IV cam is not designed for the lower compression, and will be a "turd" in a 400 with compression under 10:0 to 1.

Given your situation, your best option would be to make a careful Cam selection that will compliment your combo. There are High Performance cams designed to work with lower compression engines. These cams are generally smaller cams that generate additional cylinder pressure to compensate for the lack of stactic compression.

I am not an expert on these cams, but I do believe the XE grinds from Comp are designed and work well when lower compression is used. The XE 268 comes to mind. Again I have not used these cams myself, but read a lot about them.

I would reach out to "Screaming Chief" or "Mr Pbody" for help with a cam selection. I believe Mr Pbody has a lot of experience building engines using the Comp XE cams.

I would not use the Ram Air IV cam. I understand that the Crower 60916 has worked in similar combinations and is not as sensitive to compression ratio.