What would you pay for a slant six?

Hey guys,

I'm getting ready to post my 225 slant six engine and transmission online for sale. I want to have the buyer come out and see it run and drive, then take it out and have him return to pick it up. The motor has 15k miles on it after a stock rebuild. It has a new mini starter. It also has a 390 cfm Holley four barrel carburetor sitting on top of a Clifford intake manifold and Clifford headers. The motor runs and drives perfectly. Never any problems with it since I put it in the dodge dart. What do you think this engine and transmission setup is worth? What would you pay for it? Thanks!