A rust free body in Milwaukee??
Blown motor, trashy inside, I don't think I'd pay more than $300 for it.
Also, you know to make sure the control arm mounts are solid, right? They can look OK, but a bit of effort with a screwdriver can turn something that looks "OK" into this:
Also, with a blown motor, you have to take their word for it that the transmission synchros aren't toast. That's another weak spot.