Bill, have you ever thought of building a good-fitting rear T/A spoiler for our 1968 birds?
The one I have now that cost me zillions of bucks....sucks!! It is about .75 inches too high, it is about 1.2 inches too long, it warps after a year in the sun, etc.
'68 428 HO M3 Monster, 4-on-the-floor! Need I say more?