Where are you in MI?
There is a GREAT place in Jenison called Pete's Auto Salvage.
They have a 1983 300D-Turbo with about 240K+/-.
I have seen it the day after they brought it in. They ran compressions tests, etc. and all look good.
They are asking $500 which includes a 30-day warranty.
They are flexible on their prices...
I have no $$$interest in this place, other than I have purchased from them on a regular basis since purchasing my 1981 300TDT.
Give them a call...they are great to work with.
Their website does not show this engine in their inventory, but I confirmed that it was still there after reading your post:
616 669-6592 and ask for BRIAN.