well, sortof...
the R12 refrigerant can use all the help it can get to remove heat from the cycle, but a parallel flow condenser has one drawback, there is little room for liquid storage. the fact that a reciever dryer is part of the system helps, so it SHOULD improve the situation. the problem I can envision is this: R12 needs compression, heat removal, and flow velocity to function properly. compression and heat removal are fine with a PFcondenser, but velocity is massively reduced. I think it should improve both efficiency and cooling capability to move up to the PF, but velocity may be deminished enough to cause a reduction in capacity.
before going to that expense, I'd remove the existing coil, flush it free of residue, and chemically clean the fins and tube surface to get maximum from it.
if this doesn't help, only then would I consider a PF
if your sig pic is your car, at least you have a light color paint on the car. I'd get ALL the windows professionally tinted the max you are allowed, and do what is allowed on the front as well.