I guess that plug-welding rather than spot-welding to replace an original spot-weld would be a non-no (if you have to have factory welds)?
And, it would certainly be wrong to use epoxy primer and urethane paint when doing a full repaint?
Original primer was inferior to modern primers - what original-style primer would you recommend?
Modern acrylic enamel top-coats are readily available and closer in formulation to original synthetic (alkyd) enamel paint - are they OK to use?