remember the old saying " gotta" -pay to play, first off the only aftermarket casting for modular 4.6's are trickflow heads, anything else is just a factory ported casting pi or non pi. its same with my year 5.0 pushrods, everybody wants to cut corners save money and go with factory ported gt40 heads, but by the time you do valve jobs, springs, retainers, rockers, port work shipping back and forth if you have to pay to ship them out your talking $1,000. you could of bought aluminum head that flow same or better unported and still room to port. same goes with pi heads, might aswell find a cheap pair of pi heads to do pi swap and port them if not just spend a little more and get a set of trickflow heads. hands down fastest 2 valve cars I see are either turbo or have trickflow heads. or both.
that being said I stand by trickflow I run them on my pushrod 95 5.0 and love them trickflow all day.
I would say trickflows if you want to keep it all motor, most of the fastest n/a 2 valve cars or dynos I'v seen have been trickflow headed combos/ and or 5.1 stroker / cars.
and fastest power adder 2 valve cars ive seen have been turbo cars or ones with the torktech kits with 03 cobra blower twin screw kb / whipple or eaton setups with forged motors.
But hands down 2 of most impressive 2 valve ive ever seen was a car that had a cobra block , trickflow heads forged 5.1 motor with turbo kit, thing made 650rwhp on low boost pump gas had over 800 on race.
and
saw a 8 sec 2 valve car was a 99+ gt with same setup 5.1 stroker forged trickflow heads a huge turbo and 25-30psi thing was running 8.80's in the 1/4 .