These things are quite plentyful.
I have found two ACDelco part numbers for this.
Interestingly on Summit Racing website: "Replaced the tps on my fast BBC mpfi set up causing me issues for over a year but was intermittent so hard to trace. This tps was a direct replacement and seams to be better quality than the fast tps with a cheaper price"
It's the range we need to be testing and that will require some voltage readings.
Can I suggest, if it is the TPS maybe the underlying factor here is heat. As the TPS heats up with the engine, the fault appears. So won't take long after starting to happen, and hence why you never seem to go far. Over the year, you could well be dipping into the same couple of faulty batches of Delphi TPS'.
AC Delco have 213-895 and 213-896