Cheapest way to built a 300-350hp small block

simple.

360, 9.5-10:1, xe268h or comparable, stock 1.88-2.02 J heads (bowl porting optional)/rockers, ld340/rpm/air gap, 750dp, headers and decent ignition. Nothing fancy... 330-350hp...

One of those in a Demon with 2.94 gears/2500 converter ran 104mph in 4500ft air at Vegas... it was fat too...