I think if I bought a cossie the first thing I would do is get it checked out, make sure all the wiring and connections are all in good order, then onto the suspension and braking components, like bushes and the condition of the callipers, they are performance cars, but on the old side so often a lot of stuff could benefit with renewing to make sure they keep healthy.
I'd agree with this before looking for power, also a good set of tyres as people still manage to fit ditch finders even on cossies