If you can't do the welding yourself do yourself a favour and sell the car, save up some money and buy a better car that doesn't need rust repair.
A 383 Charger is not worth enough to justify paying someone else to do major rust repair on. This car could need frame rails, inner and outer wheelhouses etc. by the sound of it.
I think there is an advertiser here that will fix all the rust on the car for something like $20k and thats better value than a local body shop that will cobble it together. So that gives you an idea what you're looking at. No sense in spending $40k to restore a car that will be valued at $20k when finished.

Sheldon