Unless you don't mind running octane boosters or AV gas, I'd steer clear of the Aussie heads. If I remember right, even with flat top pistons the Aussies will push your compression over 11:1, and that is way too high for pump gas. Even with the quench effect of the chambers that dude is going to rattle like a jar full of marbles. The 2V heads are generally the better way to go for low end, but 4Vs can be made to make great torque; it's all in the cam timing and carefully matching parts to work together. I'd do the 2V heads and a good cam, my understanding is over .500 lift, with a low (260°-270°) duration. Amen on the .030 overbore. That is about max unless it passes a sonic check. Just my 2¢.

 

ok just to nit pick a little the 351m/400 did not replace the clevland nor was it meant to
first the 335 series was suspose to replace the aged 360/390

in 74 they stopped the clevland
1n 75 (and the next 10 years) the 351m was used to help with demand until winsor could fill demand and only emissions killed it

hey i admit it it you want a car motor that will rev up and burn the tires the 351m is not it(with out work)

if you need/want bottom-end tourque for a truck or large cars there is no more perfect engine than a 400 amazingly just what the fomoco peps planned huh?

actully i have a set i have a set of 302C aussie heads i am polishing now but am going to get a new(old) truck and garage the battered_bronco to build a short block and little body work

and if set up propery they can run 13+:1 but this doesn't work as well on a street verihickle too many varibles
i am stooting for 10.5>11:1 and with a .042 quech height it should work nicely

as for staying .030 over no doubt you got to check the thing before you bore period, but the thin 400 block can be bored .060 strength is not a issue but heat
if the walls are too thin you make a HOT engine literally boiling your anti-freeze