Running rough, idles rough, loss of power

Noticed truck making lots of white exhaust smoke in mornings, but went away after warmed up. Drove okay, but not quite right. Stopped for breakfast. Truck started right up, but had no power. When I pulled out onto highway, it just crawled. Kept going, and after a mile or so got power back enough to get up to 55. Took it to the garage I use, and they said I needed a new distributor. Did that, but it did not really help. Still not running or idling correctly, but they gave it back to me as "fixed." I took it back, and they claimed defective distributor and put another one in. Evidently that did not work either. Got a call yesterday that I had a worn crankshaft that was messing up the distributor.

Now they want to replace the crank. I watched your 454 rebuild videos, and I'm not sure that is a good idea. Complete engine rebuild, maybe. Just putting a crank in a 240,000 mile engine so I've got a new crank and everything else is 240,000 miles/23 years old? Who does that?

Asked them to price a Jasper remanufactured engine as well.

She is a crew cab dually and my baby. I briefly checked Autotrader, and a 2000 crew cab single rear wheel was $18,000.00.

Recommendation?