I have a question.What are GT heads for a 390? Are they better than stock truck 390 heads? Will they fit my truck 390 block? Help!

 

depends on the casting number some GT's came with the C8AE-H just like some pickups

 

I believe 390GT heads had a different exhaust pattern to fit in the Mustang engine bay. The heads would bolt to your block but might need to change exh. man. There is little performance benefit to GT heads.(this should start something)
Some mild port work on your truck heads would be money or time better spent than changing to GT heads.

 

The only difference with GT heads is the 14 bolt exhaust patttern and slightly stiffer valve springs to go with the GT cam.

barry