how to make a 6.1 spin safely 7500 rpms?

vntned said
Trade it for that GT350R Voodoo engine 8000rpm+ stock!!!

There's a good article in Hot Rod on spinning the 5.7 and 6.1 at high RPMs

Weak links in the 5.7 and 6.1

Hypereutectic pistons

Stock Hemi main caps break at the 800-900 hp level. Easy fix is a Arrington main cap and ARP studs

Oil pump pickup tube failure. The 6.1 has a added retention tab.

Stock powdered metal rods fail. Forged rods are the way to go

Camshaft options are limited due to variable cam timing. Stock springs are also heavy. There's a kit available from Comp Cams (Cam Phaser Limiter Kit)

Stock cast crank bends at the 600hp level on the 5.7. 6.1 has a forged steel but and aftermarket replacement is recommended.