Between the TF and SM head? A BUNCH! In favor of the TF head...but I don't feel that's how they should be picked. If you were to buy both heads complete from their manufacturers, and take them apart...you'll quickly see the TF heads are much better for the money.
Hand ported, the SM heads can make real good power as well, but after all the extra work, will probably cost as much or more than the TF heads that you can buy and bolt on asap.
Only thing I haven't done yet is re work some TF heads...I'm sure someone will want us to, but so far we've made 532HP with pump gas and hyd. roller cam in a "streetable" combo with power accessories and low stall converter app. Still using a dual plane intake as well.
We might be doing a more robust build here shortly, single plane intake, large solid FT cam and even maybe do some work to the heads in search of 600HP on pump gas. I think it'll make 580 no problem, but that extra 20 will be fun to hunt for.
