Good heads on an FI engine allow you to make more power at lower boost numbers. A good example of this is my 14psi run. I made ~10 hp less than Parish on his 16psi run and I have a smaller turbo. Our cams are slightly different, but not different to the tune of 50hp (which is ~2 psi for my set up). And my numbers were AWD on a mustang where Jim's where 2wd on a jet. We have other differences obviously, like tune, injectors, etc., but you can see that there *is* actually a big difference here due to my heads.

So which was more cost effective? My TEAs vs Jim's big turbo... The turbo was probably cheaper and a pulley definitely is

As Mark already said, if this is an all out effort get some high dollar aftermarket heads. If this isn't an all out effort, either get some 317s or keep your stock heads, and invest in a bigger pulley.

 

The original plan was to buy some used heads, rebuild them with good parts along with a full port polish and swap them at the same time I do my cam. I have thought about some good aftermarket heads but I have no idea who makes good heads for the ls style motors. I am already running 10# of boost, My only real goal is 500hp and 525tq to the wheels. I would like to be able to run a mid 12 with a good 60' time. In order to make my goal I need to make ~ 90hp and 75tq I still have some inprovements to do which include LT headers, dyno tune. I am still using the predator to tune the best I can. Would it help me any to have the s/c port matched when I do heads?

 

Honestly, you should make 90 hp or close to it by doing the tune, headers and cam IMO

 

As I've said before. I made 445rwhp 489rwtq with a 216/224 .558 .558 114lsa cam, pace setters and ORY pipe, lots of meth (100%), custom larger intercooler, & 12.5 psi with a 3.0" pulley in cool weather. I was running as much as 31* timing and backed down to around 26* above 6k due to kr. If you want 500 rwhp on the 4.8 you will most definately need good heads and more boost. Good luck! My next step was going to be a 2.75" pulley before it detonated on a warm day and busted 3 pistons.