This is anecdotal but the Mexican 043 has the best port design out there. Also has very similar characteristics to a stock head as far as cooling is concerned. Some renowned headporters in the US are making a lot of power with these heads.
The 041s are good, if you change the seat and valve in the exhaust for a larger one (35.5). My understanding is that the 39 x 32 design was to create extra heat to lower emissions. It is a mismatch in valve sizes for a performance (or any) engine - they will work, but you could do better.
The 044 is the head that is used most extensively, and there are plenty of people making a lot of horsepower with them. Probably the CNCed 044s (round port) would be the best bang for your buck.
Its where you make or break the engine - pour as much money as you can afford to into them... Theres a good article in the tech section of
www.cal-look.com .