Ok, this might be a dumb question but why do you think you have messed up the rings? Is it missing really bad? Smoking badly? It might just be a blown head gasket which would make it miss and produce thick white smoke I.E> water in combustion chamber.
Iron headed motors are pretty forgiving when it comes to over-heating, rarely can you get one hot enough to seize rings on the lands, but popping a head gasket is fairly common place. If you have messed up the rings which I doubt then you'll be tearing it down for a rebuild, there is no magic cure.
Remove all 8 spark plugs and do a compression check and if you have any that are low, squirt some oil in them(about 4 good squirts from a oiling can) and if they come up after putting oil in there then its a ring problem.
I'd also do a cooling system pressure check.
Keep us updated.
Cp