Been a Long time since I worked on an 85 and older trans and I'm 99% sure but figured I'd post this up as "good info" anyway, since I searched and found Nothing on the subject.
15 years ago or so I had a customer with an 85 turbo Daytona that had a bad vibration at idle and i'm pretty sure (not 100%) it vibrated up into the rpms with throttle. After a bunch of obvious diagnostic, and knowing the car had just got this problem after having a clutch installed, we went after the clutch/ PP as posssible culprit.
Turned out that someone used an N/A 6 bolt flywheel to replace the turbo flywheel. Since the older mtrs where Externally balance by the flywheel/ ring gear (this is what I was told at the time) it shook being missmatched.
Sure enough, we found that there were two different part #'s and a pretty big difference between the two flywheels. We put the right one on and problem solved.
So, here I am with an 85 that's being converted to 5 spd and I need to make sure I put the right flywheel in there!
I have both 6 bolt flywheels and I'm 99% they go like this Turbo = part#4329179 and has smaller "ring" on the backside AND takes the larger PP bolt pattern.
N/A = part#5222680 and has much larger (thicker) "ring" on backside and has smaller PP bolt pattern.
Someone want to confirm 100%?
Also, was the 2.5 Ever available with 6 bolt flywheel? (that could throw another wrench in there!)