I am engine-swapping an 88 Duke/manual powertrain. My engine will be available, once I don't need it any more.
The down side is that it's going to be several months. I haven't even started mounting the swap engine to my spare cradle, yet. (The plan is to build it up, then do a hopefully quick cradle swap.)
The up side is that it's still in the car, and running, so you can hear it run or even drive it. I'll probably drive it to the club meeting, this weekend.
It has ~155K on the odo. I have only put a couple thousand miles on it since I bought it, so I have NO idea what's been done to it, prior to me buying it. (The suspension was completely shot, so I'm guessing only the bare minimum...)
I replaced the timing cover and crank seal, a while back. I can tell you that the timing gear looked good, when I had it apart, but I don't know if they start to look bad before they fail, or if they just frag, all at once. It still probably needs a rear main seal. But that should be the last leak, and will be an easy fix if you're swapping, anyway.
Take all that for what it's worth.
Edit - A bit of unsolicited advice. If I were looking for a replacement Duke engine, I would first try to acquire one of the crate engines like Ralph is buying. (Last I heard, there was one more left, but that was a while back. It could be gone by now.)
Barring that, I would look for an 87 VIN "R" Duke. (This includes the Fiero, as well as several FWD GM cars, including the 6000 and the Celebrity, I think.) The 87 has DIS ignition like the 88, but doesn't have the goofy force balancer that the later engines have. It will be nearly plug and play, with only minor differences. (Keep your old engine until the swap is done, in case you need to steal any sensors or fittings from the 88.)