Factory stock original 383 4spd fastbacks can go for as much as $65 grand, yours being a little off original with different drivetrain and things and you having the original drivetrain available helps a lot. Should bring in around $26-30 grand easy if its really clean and not cut up or ever been wrecked or rusted out. Looks very clean. WHats the E-body you are looking at?
What issues with the 383 for it?