I just bought a set of trick flow heads dont remember the numbet but it ended in CO1 and they are bad ass they are the cnc ported version they were a little more expensive like 18-1900 but they are sweet....you can get a set of twisted wedge heads for about 11-1200 bucks that are bad ass but gt40's are a good head for the money I had a set and had them ported and polished and they were great
The GT40X heads aren't terrible heads if you can find them decently cheap. I put them on my 95 GT with an E303 cam, Edelbrock Performer intake, and all the other bolt-ons and made 275 rwhp on the first dyno pull completely untined on the stock EEC. They are easily capable of 290 rwhp with a good tune and the right supporting mods.
i have the gt40 intake and i was thinking bout getting the gt40x aluminum heads in the future.. good idea or should i get something different
It depends on what your performance goal is. The combo of GT40 intake and GT40X heads should give you good pulling power up to 6000rpm while still maintaining good low rpm torque. The stock cam with 1.7 roller rockers or a mildish performance cam would work very well with these heads and intake, and 300rwhp is certainly within reach.
The TFS TW, AFR 165, Edelbrock Performer, and Holley Systemax heads will outflow the GT40X heads and yield more HP (TFS TW is the king of this bunch), but the trade-off is a loss of low rpm torque.
Decide where you want your powerband, choose the H/C/I combo that'll get it for you, and gear the rear diff. to optimize performance with that combo.