Stock vs. steel vs. aluminum main caps

.................The time is now.....400 block 511 stroker callies crank, diamond pistons...my buddy has had problems with the main caps moving around on the same build twice 1st time with a dyno'd 513 hp 620 tq, had ARP bolts , now with ARP studs and stepped up to 650 hp and 670 tq built by pro's it will be gone thru over winter again...I would never want his grief or expense....kim............