This is exactly what i'm planning on doing... I have a PMR engine and fear the rods. Before i mod it and blow it up, i'd sooner pull it, and change the rods. I found a GREAT deal on ebay i couldnt pass up, 8 forged rods, 8 coated (top and sides) pistons, new push rods, and amazingly a custom grind cam. This is about all i would heed in the bottom end except maybe main studs, and coated bearings as well. Once i get my Terminator, i'll save up for head studs, valve springs, and bore/hone the engine. Once i have the parts, i plan on getting the engine balanced, and then swapping out the old stuff for the new stuff. Break in the engine a little bit with stock injectors, and do like JW did, swap in big injectors in the future when i recoup my $$.
Side note- just wondering what, if any, tuning changes need to be done for a custom ground camshaft?