LA block hunt/search maybe shift to piston hunt

You could do a number of things. One is a custom piston may be the easiest like a Chevy 350 piston with Mopar 18 degree valve reliefs. If it is a mild motor you may get away without changing the valve reliefs at all and run a stock Chevy piston with enlarged piston pin bore. Or you could grind the crank to Chevy 2.1 journal size and run a Chevy rod and piston. Lots of paths to follow.