I saw no mention of rear in gears in your post or sig. Some 3.55 or 3.73 gears are almost a must have beforeyou think about different heads. Any high performance head will move the power band up in the RPM range. With stock gears, that means the engine will take longer to get up to the point where the engine starts to pull hard. Once it does get up to that RPM range, it will run good, but below that RPM range, the stock heads will pull just as good, maybe better. A new intake manifold is also a must have with new heads, otherwise you just moved the flow restricting point from the heads to the intake manifold.
Here's something to think about:
Trick flow's are great heads. But You need to buy new stud mount rockers & new special length pushrods. Not only that, but you need to use an adjustable pushrod to figure the proper pushrod length. If you are a very good mechanic and are careful, this is not a a big problem.
http://www.trickflow.com/
AFR heads flow the best out of the box of any aftermarket head. However, they are $200-$300 more expensive new than most of the other aluminum heads. You don't need any special pushrods, but you will need some good roller rockers. Stock rockers can be used, but that takes away from why you got the heads in the first place.
http://www.airflowresearch.com/
Edlebrock makes good heads that cost about the same as Trick Flow. They don't flow as good as Trick Flow or AFR, but they don't need any special pushrods and use regular pedistal mount rockers.
http://www.edelbrock.com/
Thumper heads are ported cast iron heads, and are a great bang for your buck. This is the best budget head you can get unless to snag one of the 3 brands of heads above from someone who needs quick cash. The Thumpers don't flow or make as much power as a good aluminum head, but they have lots of kick for a street combination and are as easy to install as stock heads.
http://www.thumperoforangepark.com/
There are lots of other head makers, Canfield, Brodix, Dart, Ford, Holly. Pro Topline, etc. See
http://users.erols.com/srweiss/tablehdc.htm#Ford for a flow chart comparsion.
