I have always been partial to the 383 over the 400, I like the larger journals.
Compression adds quite a bit of power, many years back I was running a 302 Jimmy out to 320 trip two barrels and a Schaller 1/4 speed cam. I popped a head gasket and while it was apart I had the head shaved .080, the Jimmy was in a very lightened 38 Chevy coup which was running very consistent 14.3 14.5. With the shave job and a little better tire I could on a good day pop into the upper 13's, but more of a kick was beating a buddy who had stuffed 265 in a 52 Chevy. He was the first to beat the krap out of his firewall to stuff a SBC in his car, A month later with some massaging to the 265 he blew me away getting into the lower 13's.
Phil
No matter what your beliefs are "GOD BLESS AMERICA"
Fully retired marine tech near 60 years in the biz.