i did a little math and think the hemi is probably going thru the traps at around 6200rpm. that would really wring out a stock street hemi from my back in the day experience. the chevelle was probably doing 7300rpm. the 375-396 in factory trim would do 6500rpm (basing this on a friends '68 375hp chevelle from back in the day). the 396 is making power thru rpm. keep in mind those BBC had big port big volume heads, more compression and cam than anything mopar had. i do think that power was close to the same for both. i estimate about 525hp which would be a big increase over true show room stock. as far as street racing went in the '60's those solid lifter BBC did run very good; especially in light novas and camaros.