Unique Situation. What’s My Best Truck Option?

We don't see the truck, we don't know it records and we can't predict reliability.
Unfortunately with older vehicles it is common that when you put $3000 into clutch, the transmission will give.
You spend $4000 on transmission and then AC will start blowing hot.
If you don't feel like making the assessment - take it to a good mechanic.
Or just park the truck under the camper for 2 years.
I did lot of projects in my life and rule of thumb is that what is estimated for 2 years, usually takes 4.