I think you'll be ok, I put stock 318 heads on my 1984 W150 with the exact same cam you have, along with flat-top pistons to replace the dished stockers, worked well in the low to mid range, nosed over pretty good at 4000 rpm's, but I didn't mind, worked great in my 4x4. Your heads with bigger valves and some port work should be just fine. Good luck!