stock duramax rad is bigger (by about 10", but thinner)than M715, but smaller than 8.1L stock GM rad, same with dodge cummins,diesels seem to have smaller radiators, so I'm figuring the diesel will run cooler, not hotter, i may be wrong, but that's the impression, either way, lots of guys have 440, 460, 455,etc in M715 with no cooling problems, I just got back from visiting a buddy in Phoenix, he's got a 460 outa a 2000 FSD in his, it was 115* out and his truck ran a perfect 180* all day while driving around. I'm planning on using a 3 core for a 396, it cools built BBC.( and fits the M715 radiator support, after a little modification) so it should do a stock diesel...but you never know...thanks for your concern, I'll do some more research...