451 Budget builds?
with a big block...get better heads, then save in other places.
about 280 cfm with stock valves and ported is all there is, after that...it's just cheaper to buy a set of stealth heads for $900.
I think KB has a hyper for the 451 using the longer 440 rod, I would skip the 400 short rod idea.jmo
it's a faster rev'in 440...