I chose the 451 over a 512 because , I just don't need a maximum power engine, I really like RPM, and the 451 combo is lighter and shorter.
I'm lovin the extra room in the engine bay... not a ton but now I can change plugs without too much hassle and the headers aren't so tight they knock the shock towers!
Plus, I kept as much from the 440 to transfer to the 400/500... the distributor was NOT one of them. Also, watch your alternator bracket mounting height changes. A couple of minor things in the grand scheme of things!!
ALSO!! My Lunati solid lifter cam makes enough vacuum to power my brakes and I am having no "street manners" issues with it so far... It's really fun to be cruising along in second, build up some RPMs while doing 35 and stomp the gas and smoke the tires... as you get into the cams "happy zone" the motor REALLY comes alive!
Lunati Voodoo solid 3 bolt cam
Part number 60342
Thinking about it again makes me do my little evil laugh