I'll back the no conversion idea if you're on a tight budget.
you can have the 3.5 or the 3.9 v8s with no major dramas and I believe that one of the buick engines will also fit in but since its more or less the 3.5 in disguise theres not a lot of advantage to it.
depending on how much damage you did to the original when you cooked it you could get away quite cheaply with a do over of the heads and the headgaskets.

