Brad - Sorry to hear about your experience, Bummer! big time. Over the years, I've owned and driven 21 Westies.. Bought, sold, rebuilt -Etc. I try to be as honest as I possibly can with prospective buyers. One trade comes to mind re an 84. I had used it as a daily driver for over a yearran well and was properly maintained, Was approached by a college student - He drove it for a few days, on a trial basis, and come back with glowing comments. After he purchased it, he loaned it to his live in girl friend. A leak started at the hose/radiator connection - just a seep she said.  Well after the engine froze up and had to have an engine rebuild, he came back at me to help pay for the repairs. It was a sad experience - police called, etc- The point I'm trying to make is  - there is such a thing as an honest mistake -and no matter how hard we try to be at peace with it - when we start having to pay for the repairs, it's hard to accept the fact that we had a part in the situation and that it wasn't all the other persons fault
None of us has escaped that part of the trading process.
Good Luck and all things being equal, ie no rust and good condition etc, I would opt for the TIICO.. I think the conversion kit is available as a separate item.. As for selling as is - There was a very nice one in Seattle about a month ago that sold for $750.00 with a non running engine don't allow one deal that went South, change your personality, There are lots of them waiting patiently for us to come along.  :-)
Bud Yandell