Glade I could help some.
FYI the gt-40 heads use the same header as any 302 so theywill work fine.
The gt-40p heads came on 95 up expolrers with 5.0, they are the ones that use different headers.
If you are going to put a cam in the 86 motor at least make sure you upgrade the springs alittle.
One over rev with some valve float and your touching a piston.
Actually the 86 cam workes the best of all stock cams.
I would just leave it in there and spend the extra money saved on something else.
If you spend some time on the web at

www.corral.net

And do a search for 86 cams you will find the guys are making real power with the stock cam.
Good luck with the build!