1974 Rear Spring Shackle Removal Problem

[LynnJr]

Guys I had my entire frame powder coated in gloss black and now I can't get the rear spring bolt out of the shackle to replace/upgrade the bushing.
The nut has been removed but the bolt won't budge at all.I think it is locked into the rubber somehow.
I can't use a torch as the powder coat would melt.I tried beating on the exposed section of the bolt but it hasn't done anything.
Any ideas on how I could get this bolt removed without damaging the powder coating?
Lynn