rear control arms

will 5.0 after market rear control arms work on the turbo coupes

I assume you mean 5.0 Mustang? No, Mustang uppers way too short, lowers about 3/4" shorter. Using Mustang lowers will change your pinion angle to an undesirable angle.

Check out CHE Performance for uppers/lowers, Maximum Motorsport for lowers.

Do a search, there are some GM uppers that are close.

Hey Robert , do you know on how far you can lower the car before it starts throwing off the Pinion angle, and witch rear arm do you have to get to put it back in the safe mode . Thanks, i lowered 1 of mine and it all looks good , just dont want to screw anything up . My Blue 88 I did have to replace the U-Joint in back by the hog , went bad , my guess is due to it being super lowered , I did change it this year , the rear springs .. , so Im good on that car . Thanks for any help . D.Wilder

No, I don't know when lowering will affect pinion angle adversely. My own experience is with the FM 5300-D springs, made for pre 87-88 Birds. It lowered mine about and 1 1/4 and did change the pinion angle enough that I picked up some noise. I used CHE double adjustable uppers and set it 2 3/4 to 3 deg. The only spec in the Ford service manual is driveshaft to pinion shaft. No mention of transmission shaft to driveshaft.
The actual spec. is 2 deg, 40 min +- 1/2 deg.

I used a digital level from Sears. Get the car up on jacks or a lift if you have access. Measure the driveshaft angle using the level on the bottom of the driveshaft. I removed the pinion yoke from the pinion flange and then measured the angle of the pinion flange face. Draw yourself a little diagram and you can figure the relative angle from those two measurement. The outside face of the U joint flange on the pinion yoke is not machined or square with the pinion shaft centerline. That's why I use the pinion flange as a reference.
Be sure to mark the yoke to flange with a reference mark and reassemble with the mark aligned.
It did have a positive affect on the rear end noise. Not earth shattering but noticable.

OK, will try to look into that , I had my just way to low , so i changed the rear springs again, had used the Motorsport spring from Ford , but were from a Stang , witch ment that they were going to be low or lower than using them on a Stang , looked nice but , after a summer , had to change the u joint up by the hog, and for sure was a angle thing , due to the lowering . Thanks for the reply . D.Wilder