Oh - somehow I thought the original engine was gone. Dunno how I thought that - guess the "roller" in the title threw me off. Now you're entering into the above mentioned collector zone that a12 was showing up there. I wouldn't toss more than $10 tops and that's if I really wanted it, but there are going to be those that will throw the $14 or so at it. Then the restoration will eat them alive and the tears will flow.
I've got 2 1969 runners, much like the red and green GTXs a12 posted. One was pretty straight and had a few minor accidents over its life and the other had a much harder existance. I chose to do the better conditioned one first as I thought it would be cheaper. Well the same amount of parts replaced is the exact same - or near to it. Complete rebuild of entire driveline, complete interior redo, straighten and rechrome, replace trim, all new fasteners, complete electrical going over, etc., and the differences in the body effort would only amount to a few grand at the worst. The main difference was that the garbage parts pile was in better condition than the garbage parts pile from the worse off one would have been.
So it really is false economy if you look at what you want to do and what parts you are replacing. A quarter panel replacement is the same cost if it is not too bad but should be replaced, or a beat to death item. Hidden rust is the unequalizer.