With flat tops your compression is closer to 8.5 to 1
if you switched to a smaller cc head like a 64cc you'd be closer to 10 to 1 and much better off.
Try flashing the rpm's higher off the line to get into the powerband of the tunnel ram. Also running that open exhaust is killing some torque too. try running a longer header extention pipe or some racing muffs.
Nice looking old school Nova.
Trick overflow too....lol