i priced a new engine from a [Cummins] distributor - IIRC, it was ~$6900 (12 valve, oil pan to valve covers, includes fuel system and turbo, 215hp rating).
i ended up getting mine rebuilt (including new pistons and rods, +.040", and some tweaks including new injectors and DVs) for $4500 through a local shop. this normally isn't needed, but my engine was abused in it's previous life (timber company with hundreds of hours of idle time).
[on edit: oh, this cost also included full R&R by the shop + warranty]
normally a used motor would need rings and a light hone (and maybe head re-surface while it's off). i don't know of cost for this but wouldn't imagine more than a few bux and your time.
otherwise, source the correct SAE engine adapter, clutch/flywheel, and a motor mount and you should be in business if you want to keep the Spicer. if not, then things get interesting...