C4 in a 99 4.6L with long tube headers?

I am not sure. But being that its smaller in diameter it should be able to clear the tranny. :shrug:

Theres other companies that makes headers that fit under the 4R70W. You may get them if youre worried about not clearing the C4. Just a thought. Also theres some guys in www.modulardepot.com that use the C4 tranny. You can ask there if you dont get much help here. :)