Id consider a 360 core block due to the fact stoker piston offerings for the 318 are slim these days and costly. Also im not sure id use a 2618 alloy which some of the current 318 stroker pistons are, in a high mile build, Ive one with icon 2618 forged at .005 cold and it rattles cold, rattles hot, ect.

360 stroker pistons/rings can be had for about 1/2 of the 318s cost.

Id shoot for 20 more inches and reduced cost.

Good luck.