Should be very easy getting 400 rwhp, my guess, around 470-480 at the flywheel, very easy to do with a 440, This can be done with factory pistons & bolt-ons/cam change on the pre 71 short blocks, if not, this is what i'd do for a later block.

.030", TRW 2355s, block prep.
Cleaned up 906 or 452 heads (decent VJ) no porting
XE274H or 275HL cam & springs
True roller chain set
TRW oil pump, doesn't need to be high volume.
1.7/8" headers full length, or even Shoe-Mack.
2.1/2" exhaust.
SD intake or RPM.
750 3310 vs. only because of the gears/converter your useing.
Good ignition with a nice adj. timing curve in dist..

The car should easialy get into the 12s in a B body. & be VERY street friendly, i'd run pump premium.