The CV joints used on X1/9 vs Scorpiacarlo are the same 86 mm bolt circle and interchange quite identically since they are the same part. The Lancia uses a proper bolt/nut joint for all the CV joints while the X has threaded drive flanges that can result in loose CV joint bolts. X owners should check the CV bolts ever so often as they can and do get loose.
If needed, I have nice MS2125012 point cap screws of the proper length, MS20002C countersink washers and matching Kaynar 12 point nuts for this specific CV joint and drive flange combo. Send me a note if interested.
The axles are differnt on the Scorpiacarlo, one of the axles is a hollow tube with the spline ends welded on. The other is near identical to one used on the X, a solid, splined end axle. The hollow, welded up axle used on the Lancia was done to equalize the axle twist under driving torque. This helps both driving deliver identical wind up and torque to the rear wheels. It's is longer than the similar axle on the X.
Just recently, we had a set of Nissan Q45 axle modified (shortened, spline ends cut with snap ring grooves) for the TR6 by Moser Engineering. They did quite well with this job as the Nissan axles were heat treated. I would recommend them if custom axles are needed.
Yes, we are converting the TR6 U-joints to CV joints and Nissan Q45 LSD diff.