Technical Clutch fade when hot. I'm sort of out of ideas.

Good call! "Now that's thinkin' with your dipstick, Jimmy!"

 

But wouldn't a cracked weld or broken part affect the shifting hot or cold ?

 

I would think so...Maybe trans oil temp a the culprit..

 

Change the pressure plate. It's getting hot and becoming a dish. Flat when cold dished when hot then you don't have enough surface to prevent the disc from slipping. Note: I personally have never had a bronze pilot bushing seize an input never. If that was happening the T-10 input would show that!

 

OP didn't say clutch slipping, more like dragging..

 

Laugh at the cracked z-bar... I had a '64 Galaxie when I was like 21 and I had an issue with the clutch not fully releasing and when it was fully warmed up, it was worse. So I'm thinking the TOB is bad. Out it all comes, old TOB doesn't look terrible. Get it back together and when I went to adjust the clutch, I found a tear in one of the z-bar welds. So now, I look at all the externals before I look at the internals.

 

No laughing, friend had a 66 F'lane that had the two piece Z bar that was tearing at the joining bolt, driving around hot or cold was fine with normal clutching but power shifting it caused missed gears...