Here is some info passed on to me by 800xl, i hope this helps. And i hope 800xl doesn't mind me pasting his words.
Will it bolt right in place:
VERY, Very likely. I have not had one sitting down on the motor mounts in a LUV yet, but everything looks like it will line up. As long as you are looking at a 76 and newer 1.8L, that is. The 75 and older trucks have different motor mounts and the trans housing is different as well. (starter on wrong side) The best match would be a 2.3l going into place of a 78-82 LUV. 76 and 77 transmissions have the clutch on the other side, so mounting of the slave cylinder could get funky with the 2.3L Best case would be to get a 2.3L with a 5Spd trans to match, though you have to shorten the rear driveline.
Is it reliable:
Yes. Though keep in mind the only one I've owned is down right now with a blown head gasket, at least. They are much like the LUV 1.8L, keep the valves adjusted and make sure your cooling system is clean and working right. That and regular oil changes will keep a 2.3L going for a long time. I got bit by an old chunk of heater hose that blew out on my 2.3L. Once a bunch of the water dumped overboard, the head gasket let go quick. Keep it cooled and there are not many other things to worry about. I've only seen a few with a blown up bottom end, just plenty that had head gasket issues or cracked heads from not adjusting the valves for 100k miles. You do have a timing belt to worry about where the 1.8L has a chain, but they don't seem to be prone to breakage really if changed every 80k.