Daily driving an A-body
I hate to jump in late, but I did just what you are asking about, only from a dead reliable newer truck that I owed a bit on to a paid for 89 Cummins.
Here is what I have noticed. My Cummins was a ranch slave truck. Almost nothing worked, but the engine. I have spent about $300-500 and probably 30-50 hours fixing things. The engine is fine, and it runs great, but the rest of the truck needs TLC.
It is now semi-reliable. I don't leave home without tools and liquids-EVER!
I knew the risks when I did it. Driving is now a much more vigilant thing. You listen for creaks and groans etc.
Yesterday, for instance. I was driving in the rain over a mountain pass and my wipers just quit. It took some fiddling, but I figured out that it was the switch. Three parts store stops at the out of town destination and I was going. I moved the switch around a bit and was able to get home in the rain again. I should note that my wife was with me and it did create some stress for her, but we got through it and it wasn't a biggie. She trusts me for some reason.....
I live on a very dangerous stretch of hwy, and we regularly see 5-6 cars in the ditch on a 8 mile stretch of road in winter. There is also very little place to pull off in the snow.
I am a professional, and I can't be calling in and being flaky so there is some stress.
In the past for most of my driving life I have driven older, large 4x4 trucks so I am used to it.
Here is my rule for DD old vehicles: YOU MUST have two rigs or at least access readily to a second vehicle. Right now i am essentially down to one rig and it is a bit of a stressor thinking about the 89 only as a DD.
I am working on getting another rig going as a back up.
FWIW-ROB