What kind of compression snould see 97 454mag with 450 hours? I know all compression gauges are different just a base line.

If everything is O.K. you should be at 150 per cyl. That's what is in my Mercruiser book.I checked mine at 350 hard hours and it was right there at 150.
Hope this helps.

Throw away your compression guage and use a leak down guage. It's the ONLY way to get an idea of what's going on in a motor.