I have owned a 1985 Toyota Dolphin for over 20 years. It has the 22RE (Fuel Injected) engine with about 88,000 miles and automatic transmission. Its the 21 footer, not the 18 foot one. I've traveled all over the West, up and down mountains, in hot and cold weather and I've have never had a problem with it other than replacing a fan belt once. They are very reliable, stout engines and I wouldn't hesitate to go anywhere with mine.
The first year for the fuel injected engine was 1985, before '85 the engine was the 22R and before that, the engine was the 20R. Later, Toyota switched to the V6 about '89 or '90. If you keep your speed down to about 55, maybe 60 sometimes, you can expect to get about 15 or 16 MPG. Much above sixty and the MPG drops quite a bit. In the mountains, I'm often down to about 30 MPH, depending on the steepness of the slope but the little jewel always makes it just fine. If you find a good one, go for it.
John