Don, your SCAT 340 main crank is'nt anywhere near 70 lbs....

Callies 4" are usually in the 52-53 range

SCAT & K1 4" 2.50" mains in the 59 range, 360 mains around 61

SCAT offers 2 lightened versions of the 4", I sold Scott his, I think it was the mild lighten job & forget what it weighed before I shipped it.

Callies can do a sprint car lightening program on the Magnum stuff, & get them in the upper 30's with full aero wing style counterweights, star flange etc. Not cheap... & certainly not worth much ET at all in a high 9 sec combo.

Vacuum pump would be much better place to spend your $ than a light crank if you're looking for ET, especially with a light ring pack in your motor.