Slant 6 worth?

A friend of mine has a complete, running /6 & noisy but working 4speed O.D. 833 attached to it from a 2wd 76 D-100 pick-up he has. We are installing a 6.4 HEMI & 6speed in this truck. The slant 6 has an aluminum Offy 4bbl manifold & Holley carb & factory electronic distributor. He wants to sell as a complete package not part it out. What do you all think is a fair asking price for this? I will get some photos of it TODAY & post them when here from you guys what a fair price would be. He wants it gone ASAP as far as I know.
Thanks all for your input.