I previously owned a diesel 80 (5 speed 92 from Europe, basic model with barn doors and rubber floor). The 1HZ inline 6 cyl engine was very smooth, and got good mileage (around 20mpg highway). Darn thing had a timing belt though. Yeah, go stock if you can. I was lucky to get the 92, a serviceman had brought it back to Canada from the UK (but oddly enough it was LHD). Sold it in a fit of crazyness, wish I had it back... I don't know about RHD, I don't think I'd want to own one in N-A myself. Getting conservative in my old days I suppose.
I suppose that the 5mpg difference may be a big deal for some, but I don't know if it's THAT big, especially when the tide turns and diesel all of a sudden sells for a fair bit more than gas. And it seems to me that the 80 gas engine is one tough puppy with plenty of torque and pulling power, so not sure if a diesel brings that much more to the table. Anyway, good luck with your search.