The only answer I found for your question of "Freeplay at the Clutch Lever" is not measured at the clutch lever. I reviewed Pantera Technical Service Bulletin No. 10, Articles No. 88 and 89, 1/25/74. Clutch Adjustment: measured at the push rod to the to the slave cylinder, there should be 0.102" - 0.106" gap clearance. Clutch Pedal Height can be varied by adjusting the clutch master cylinder push rod length, Optimun assembeled length 2.9" with a range of 2.91" - 2.95", the Figures with Illustrations are Fig. 15, 16, and 17., pp. 8, 9.
But you said there are only 3,000 miles on the rebuilt ZF and you just got it. So, you should know if this problem happened before or after your acquisition, I presume. Presuming it was working OK when you got it, and you didn't take it to the drag strip, it may be a similar situation to mine. My ZF would hardly shift, it was really stiff. As I drove it, and didn't mistreat it, it just got smoother and easier all by itself. I think it sat around for many, many years and the fluids settled, possibly leaving some deposits behind inside the ZF, but as things have been circulating nicely and regularly, it has really loosened up and is almost like my 2001 Toyota, really easy to shift.
Have you been driving it a little on a regular basis, letting things wear in nicely on the new rebuild? Maybe it's still tight and needs to break in a little....
Best of luck.