I do a lot of welding at home, mainly heavy stuff for my dad (he breaks a lot of his old farm equipment) and I can hold my own with a MIG, but I am by no means an expert. However I am restoring a '66 and am almost finished with my structural welding which means bodywork is next. The only advice I can give you would be, like tumbuk said, use solid wire and gas not fluxcore. I picked up .024 solid wire for my truck. I'm not sure how much research you have done on bodywork but from what I have read, and the work I have done, go slowly on the lowest heat you can and only weld about an inch or a little more at a time and then switch to another section. By slowly piecing your weld bead together and allowing each part to cool before welding more next to it, you avoid over-heating the metal and causing it to warp. Another thing I read somewhere was to weld the back of the joint where you won't see it, and then any lines or small gaps left on the front can be filled in with a little body putty. If you did that you might be able to get very good quality results without paying big bucks at a body shop... just a thought.
But hey it sounds like a very fun and challenging father/son project, should be plenty of bonding time for the two of you and lots of good memories
Best of luck with it!
Nathan
