Greenwater
The cost of the kit is only a small part of the upgrade in my experience.
I put a twin-turbo kit on my FFR - 302 EFI. Even after the obvious upgrades such as 70mmTB, 73mm MAF, Cobra Intake, head porting, headers and F cam I wasn't ready.
Had to have 38 lb injectors ($350) and a 255 lph fuel pump ($130) and adjustable fuel pressure regulator ($50). Then there was the ignition controller ($400). I have the Jacobs that has an in-car control panel. I can tweak timing 0-15 degrees, change my rev limiter and most importantly set BOOST retard 0-15 degrees.
But, cruising in 3rd gear at about 2500 rpm, mat it and you will fight to keep you head from bouncing off the roll bar. As a buddy of mine says "It flattens your eyeballs"
Sure is fun.
Later,
Mike