It is worthwhile to consider measuring the thickness of the flywheels and compare them. Aluminum v steel/iron.
There may also be a variation of the thickness of the mounting flange to the crankshaft or even the tolerance that the stock crankshaft flange is machined to? I haven't looked for that since you would need really more then two engines in one place to compare that. That would effect the dimension available for travel of the throwout bearing.
I do remember Gratiot Auto Parts in Detroit selling their "Pro-Stock" line of rebuilt clutches.
They would resurface the pressure plate also like you would do with brake rotors. That would contribute to more clearance for travel and it is so tight in a Pantera that even a few thousands help although we are probably trying to gain hundreds in travel?