I ran into a similar issue with my Champion using an OEM-style plastic reproduction shroud. I trimmed the shroud up pretty good and made some mounting tabs out of sheet metal & some pop rivets. It took quite a bit of "fabricating" to get everything to line up right. The hardware store window sealing foam tape is a really good idea.

70 Roadrunner convt. street car 440+6, NOS, 4-spd, SS springs '96 Mustang GT convt. street car '04 4.6 SOHC, NOS, auto, lowered "Officer, that button is for short on-ramps"