i ment clean of the rust and ark weld the gaps in, and weld the crack at the back. you would if you where "careful" be able to not heat treatagain after welding. just weld small sections then cover with water (after removing all cables and turning of at the mains) remove any flux dry and weld again.
will take some time to do but thats how i would do it......
hope this helps.
chris..............