We know the 58 - 42 split is based on Airframe, importing the jigs for the back fuselage ought not to be so hard, one wonders what the wisdom for keeping that work share with China was in the first place. Perhaps because the engines were being imported by China and the rear fuselage is where the engines need to sit. Now that there is news of the engines being Chinese, perhaps that aspect of risk/ politics management is no longer applicable. With regards to material of manufacture, Pakistan has the set-up to basically import the requisite aerospace grade aluminium alloy in block/ bar form and turn it into airframe structures, so assuming the rear fuselage is also aluminium alloy then that should be easy.
What is interesting for me would be other components, fuel systems including tanks, actuators, pylons, sensors, transmitters, receivers (not just radar, but rwr, iff, satcom etc), landing gear, even the infamous hinges etc. I don't think we have ever had a workshare percent disclosure on these. I'm not saying these are required to be able to say Pakistan has the full capability to *autonomously* manufacture the Jf-17, hell even the US imports stuff from dozens of countries to put together an F-35, but the project managers will know, that some from this list of components will need to be brought in-house for complete autonomy.
Autonomy being defined as 'PAF will continue to be able to manufacture the Jf-17 if Chengdu shuts down the assembly line, and diverts the associated work force and fixed cost set-up' as opposed to 'PAF will continue to be able to manufacture the Jf-17 if Pakistan were under complete and total embargo by every other country in the world'. Of course the reasonable assumption here is Chengdu will be happy to hand over its supplier/ sub-contractor list to PAF if that has not happened already.