318 stroker builds

The reason I recommend forged is the piston speeds are approaching failure point for hypers with a 4" stroke crank at fairly low rpm - 5K or so. I run KB hypers in a lot of things. Gapping the rings won't stop detonation - which is what probably killed yours. 10K miles they ran fine - they were fine. Maybe a poor load of gas or something.
On the heads - It's a waste of effort to leave the 1.88s in place and do porting. You have to sink the seats a hair to re-cut them. 400 flywheel horsepower can be reached with no porting. If I were doing it I'd have the stainless 2.02/1.65s valves fitted, and a modern 5 angle cutter valve job done, along with guides or liners, cutting the guides and spring seats, and new hardened exhaust seats. In other words - a proper performance rebuild. If you want to blend and gasket match it will only help gaurantee the 230+cfm, but no need to work the short turn or hog the bowls. My "stage II" heads are further ported in the bowls, short turn, pushrod pinch, and roof & walls. But I run a 2.05/1.65 valve package in them. You don't need any of that crap. You need solid basics.