if I swap an 88 turbo trans into an 86 turbo what all do I need for the swap

250mm clutch? (86 has a 240mm right?)

88 driveshaft? (or will an 86 driveshaft mate up)

do I need to drill some new mounting holes?

 

clutch goes with the flywheel. if you keep the same flywheel, you don't change the clutch.

yes. you'll need the 87-89 turbo driveshaft.

probably.

 

You can "upgrade" to a bigger flywheel and clutch with the '88 tranny, but, that is optional.

Get the driveshaft that matches the tranny. The splines are different. I suppose you could change front yokes, but, why. Just use the complete '88 shaft.

I didn't have to drill any holes. Nothing wanted to line up perfect, or easy, but all the bolts went into the holes as they were intended.

 

any advantage or disadvantage to 250mm clutch/flywheel over a 240mm clutch/flywheel

 

not really.