390 is similar to a 383 chevy specs wise. They 1.7 rocker ratio,when the exhaust side on stock castings are ported they breathe quite well. The power is good.
The 427 side oiler in my friends cobra kit is very drive able.It has a moderate solid lifter cam,couple little 600 holleys,makes (guessing 560 plus) good power in a very light car. Power is from 2,000 rpm up