390 vs 408
.060 360 =372cid
390/391cid 18 cube diff
Big bore with short/er stroke=hp/tq with emphasis on hp.
big arm with lil bore=mostly torque think 225 slant 6 but without the cubic handy cap.
built the same while compensating @.050 dur for the cid increase on the 390 and both having cid matched port volumes, the cid will reflect the power.
If just built the same, the 390 should make close if not more but at a lower rpm.jmo
But there too many variables.