My Grandpa had an 83 diesel Ranger. bought it brand new. He lives in Northern Wisconsin so rust basically killed it. He had almost 200k on it, started right up first time even on the colder winter days. He used it as a farm truck and also took it to California several times. The thing about finding parts is very true. right before he sold it, the gas tank was rusted out and he was having a devil of a time finding a tank for it. I think he sold it for about 350 bucks a few years ago, and it had a bad gas tank, bad brakes and a few other mechanical issues due to wear and rust.
for the engine, I believe they also put this engine in the escort in those years too.
As for being underpowered, I have driven it and I did not think it was any worse than the gas 4banger Ranger. He used his to tow a trailer occasionally as well. No problems. Granted you are not going to be outrunning very many cars, but it has enough get up and go to do most of your driving around town.
edit: the engine was made by Mazda I think
AJ