How high can ya rev it?

The maximum piston speed is about 3500 fpm for cast crank, stock type rods, cast pistons. Piston speed= stroke x rpm / 6 or Maximum rpm =21000 / stroke.
maximum rpm is 6344 rpm for a cast crank 340 or even 273/318

The maximum piston speed for forged crank, hd rods and bolts, forged pistons is about 4000 fpm so Maximum rpm = 24000 / stroke. Maximum rpm is 7250 rpm for forged 340/273/318 crank engine.

those are just safe guide lines found in most books people have spun higher, better aftermarket forgings and billet cranks can spin way higher