since posting I have found more current info and the magna charger is available for the 6.1 :-)
I will look into the others as well.
I do like the call it half throttle boost as was described to me by my GTO friend.
Is either or both roots type blowers?

1970 4spd Superbird, '69 Charger 500 Daytona clone,2015 Hellcat 6-spd B-5 Blue,1968 572 Hemi Charger,70 GTX 535 6-pac 4 spd,69 GTX 440 4-speed Super Trac Pac Car, 1973 383 Barracuda, and a couple Cummins