i have built drag engine two bolts mains. i know of pull trucks two mains that gets ran to 7500 rpm and many more two bolts i have built or help in more that 50 of them and in 20 years this is not a problem BUT CAPS MUST FIT IN THE REGISTER GOOD and if you are looking to make more than 700 hp get a better block bowtie or world or dart or donovan the bottom of the blocks are thicker and have thicker wall and make for a good blocks for hi hp and hi rpms pinning the stock caps is worth the works. why ?the caps is getting pulled down and the caps are iron and will fail at a point were a steel cap may be better to do this to or a better make of iron cap. world and donovan dose this to. so at apoint pinning a iron gm cap is not worth the effort studding the mains helps this is all you really need at the most.