I run 38 degrees on my 377" with a toilet bowl, but it doesn't help the top end at all. The only reason i run 38 degrees is that the car weighs 3250lbs and i need it for the 60' time, in fact the car will only run 125 and should be running about 128 so it's a trade off. Any more inches and i would also run 34 degrees, like we do on the 434" motors.
JMO
Zip.