Obviously, your clutch is dragging when the powertrain is hot, and there are a myriad of reasons for this. First, find out how bad things are. With the engine off and a helper pushing the clutch pedal to the floor, insert a feeler gauge blade through the bellhousing top hole, between the clutch disc and flywheel face. You should get 0.030" as an absolute minimum, and more is better. This means that one only has 1/2 whatever the reading was, on each side of the disc. To have such slim clearance work drag-free, the flywheel must have zero runout, the disc and clutch faces must be absolutely flat and there should be no runout in your throwout bearing or holder. This is normally impossible on any Pantera without modified hydraulics. Regardless of what may be wrong in the clutch area, you (and all other Panteras) desperately need a long-throw slave cylinder, available in stainless steel from all Pantera vendors for about the price of a stock cast iron cylinder. Continuing to drive with it dragging this badly will severely wear your transmission synchronizers. Last I checked, a ZF overhaul & synchro R & R was well over $2500 and only a limited number of shops can even do this job.
