F.A.S.T. Tommy would be the one I'd ask....but I'm not sure he'd care to divulge what the tricks are for his 11.40 second F.A.S.T T/A 6 pack.

The 416 is definately gonna draw the outboards open too quick for the short stroke 340 diaphagm springs, going stiffer would be a given IMHO. I'd go ahead and swap in some quick-change 'phrams while you're at it. I always start with the stiffest ones in the box and work my way down.... when the tires shred and the tack pegs like you've hit an ice patch you're pretty close

I know that big block Strokers love 6-packs, my old Iron head Stage V 508 is roaming the streets of Chi-town in a gorgeous 72 Roadrunner with a 6bbl, check with Paul Member PHJ426