Need help pricing a 355 engine for sale

I had the motor replaced in my 95 355 after mechanic 'convinced' me it was easier to buy and install than rebuild. After taking it to two other independent mechanics who broke it down and inspected, it was not nearly as bad as the first told me but I now need to find it a home.

It is out of a running 95 F355 with 32,xxx. The block and pistons and liners are all perfectly fine as well as the rods, cams and everything on the bottom end. The only problem with both heads is the exhaust valves on the #7 and the guides. I could get this up and running (both recommended given the miles, it would make sense to do all the valves while you have the labor invested) but what would be the point since I already have a running one in the car.

The last mechanic has someone interested in taking it and keeping it as a spare part source for his but the mechanic doesn't want to give me prices and get in the middle of the exchange. I've seen places that sell engines that offer a core charge of 3k (US$) in exchange so I believe it gives me a ballpark to work with but would like some experienced advice.

Thanks all

Scott