340 Roller Cam/Lifter Issues.

I would like more info on the oil pump failure? are the roller wheels a different diameter? how many thousands of those lifters out not had a problem?

Enough thousands that they changed the design, admittedly because of failures.
R&D ain't cheap, they didn't redesign them because they had nothing better to do.
Judging by the pictures, the height difference and roller diameter are substantially greater. Looks like near .100" or more for both. With such a large difference, it seems unwise to mix them with the 'old' style.