So is there an established approach to upgrading the 216 to insert bearings?
Federal-Mogul makes a set of insert bearings that can be fitted to the Babbit rods, once they're bored out a little and honed to size. The splash-oiling system remains in place, and that would be the weak link. Some of the oldtime round track racers preferred the splasher engines, believing the solid crankshaft without any oil passages drilled in it was stronger. I'd suggest adapting a high-volume oil pump to the 216 drive system, and using the extra oil flow to keep the rods well-lubed and supply enough oil to the turbo bearings to keep them from burning out. An oil cooler would be an absolute must-have item. An air-to-air intercooler and a sequential electronic fuel injection system would be nice, as long as we're pipe-dreaming!
Jerry