how to make a 6.1 spin safely 7500 rpms?

So I can see both sides of both arguments.

Arguably the old 340 is a great choice with a forged crank factory in the early days. Looking at later model LA's they were sort of crap. Cast crank wasn't fantastic but not terrible, low compression and not the greatest rods either. Head flow was fine for 1980 standards but even performance heads leave something to be desired compared to some of the newer stock heads from Chrysler and GM.

On the G3 Hemi side, there is plenty of good and bad. The cranks are decent but not phenominal. Both 5.7 and 6.1's have powdered rods that really aren't worth much. Any build should consider a rod swap and even a rebuild on a stock engine for unlimited reliability. Pistons are a huge weak link and were never meant to hold higher than stock hp levels. The bean counters rule the world these days and unless its necessary no manufacturer really overbuilds on purpose. But the same tricks used back in the day take this engine from good to wild in a hurry...but parts are more expensive.

So in my mind they are a horse a piece...you want more power out of a small block build the G3. you want easy and cheap parts but are ok with a lower power output then go LA. Either way you will be spending money machining, stroking, and replacing parts. I just think you get further along for the investment in the new platform. (not counting the hassle installing it compared to an LA that bolts in)