there is a wrong longer lever mounted , and it looks there is a redesign of the slave cylinder bracket .
the original lever is shorter and the bracket into an angle .
the adjusting bolt what is missing keep the slave away from a long distance free play .
some aftermarket slaves has a spring inside to keep some pressure on the slave lever.( Maserati )
the free play must be only a few mm .
Have you check if the pushrod system under the dash is mounted on the right way ? it's common that this is wrong mounted after a master cylinder is replaced.
Julian, bleeding is not difficult because the master is above the level of the slave, just open the bleeder on the slave and it bleeds themselves .
Simon
Oh , and remember , this Pantera came out of the States ,a lot of former US owners always chance good working original systems. Maybe they have trayed to get a softer pedal pressure to use a longer trow-out lever.