Somehow my last posts got deleted, so here is a repeat.
My thinking on going small motor was based on getting max life pout of a motor that will not overpower the tires even on a junk track, yet still make enough power to keep you at a 10.00, out of the expensive 9.99 or faster zone. One combo that would be dirt cheap would be to go with a 400 block, 7.10 rods, Ross 1.120 ch flat tops, a 383 crank cut to 3.54 stroke for 426 cubes. The biggest expense are pistons and rods, somebody will probably give you a crank! Compression with flat tops would be about 10.00, for pump 93. A 426 with a set of small port heads ought to make great power and still shift at 6400 rpm, about perfect with your current gears.