I'm doing a build on my 2004 GT's 4.6 2V and I'm gonna be running Stage 3 Comp Cams and doing +1mm valves. I need recommendations on the correct high compression piston to run with this that'll have safe PTV clearance. Please let me know.
The best piston to run in your new build is a Gibtec.
PTV clearance is a function of the cam you use, the way you phase it to the crank and entirely up to the engine builder to spec correctly. That means it is your your responsibility if you are the engine builder.
Best way to find out where you are is put a crank, rod, piston head and cams into an empty block. Use checking springs and sneak up on the cam phasing you intend to use. Place a dial indicator on the spring retainer and take PTV clearance measurements every degree of crank rotation from 5˚ ATDC to 15˚ ATDC. You will usually find the least clearance between 7˚ and 12˚ ATDC. Depending on cam and phasing YMMV.
The intake is the more likely to need loving than the exhaust.