Hi all. Read this post and just wanted to add something: Remember, the 4V heads have a reputation for flowing better at HIGH rpm's because they were always used on a smaller 351-cube engine. Put them ona 400-cube engine and the intake ports will "act" smaller as they are now trying to flow enough air/fuel for 400 inches, not 351 inches, get it? The velocity will actually increase somewhat with that extra 1/2-inch stroke. Still not IDEAL for a street "torque motor", but it depends on the build and intended use. A set of 4v heads with MPG port plates would raise flow activity and increase velocity for better cylinder filling, much improving low-end torque. Another note: bolting the close-chambered heads on an existing shortblock should be done with thinnest gaskets possible to take advantage of quench chambers, unless the block is coming out and milling the decks is possible or in the budget. I deally you want .030-.035 piston-to-head clearance, it will make a difference. Last two notes: PROPER cam selection will make all the difference with a head swap like this, PLEASE talk to a sales or tech rep at whatever cam manufacturer you choose. Better yet, call them ALL and get their opinions and then compare their recommendations. Lastly, installing 4v heads means a 4v Cleveland intake and spacers, (a few more bucks) available at Jeg's, etc, AND you will have to change the exhaust side of things as well: Headers or manifolds for a 4v head, whatever you are running. Personally, I would run a set of Aussie closed chamber 2v heads if on a budget, a good dual-plane intake, small-tube headers (velocity, cylinder scavenging) and I will not make any cam recommendations as I have seen too much controversy in the past and really don't feel like living the drama, lol. Just stick with a flat-tappet hydraulic and you will be fine for anything short of dedicated racing or bracket. That's my 2 cents, anyway.