I'm not saying this is good advice, but this is what happened to me.
I bought my 95 E350 shortie for $2,500. Brought it home and did the demolition phase (removed floor, seats, walls, ceiling) and had an empty metal shell. It sat like this for a year in my driveway, I think we only took it out once or twice. I took it in for the second oil change and found out the transmission was completely shot. It was some aftermarket custom piece of ****, and I basically had to get a new one or pass the bus on. At this point, I had already invested a lot of time and some money in it, so I pulled the trigger and rebuilt it ($3,100). Then the transmission guys discovered the rear differential was shot (which would explain the weird speedometer issues, as the speed sensor was getting caked in metal shavings). At this point, what else could I do but pay for the repair? I think there might be a sunk cost fallacy in here somewhere. So I paid for it ($1900) and swallowed the pain of now having paid the cost of the bus twice over for necessary repairs.
Anyway, I view it like this: I have my ideal bus size and form, with a great engine (7.3L Powerstroke), a brand new transmission, and a brand new rear differential for $7,500. Would I have bought it from the dealer for $7,500? Hell no, that was out of my price range. But I ended up spending that much, and now I know I have a shiny new transmission/differential. And, because I'm vain as ****, I like to compare myself to my friends who bought a Sprinter van that needed significant repairs to get it road ready, and they spent $18,000 before they even drove it home.
I don't know your situation, either financially or skoolie-wise... all I can say is that I was happy spending all that extra cash for the new combo because 1) I had already invested significant time into the conversion (with the demolition and painting), and 2) the bus is my ideal size, shape, and form for my conversion goals. If you haven't invested a whole lot of time into it, and if it only sorta meets what you envisioned for your skoolie size/shape, then maybe it would be good to cut your losses and move on. I've had a few experiences like that--I spent $600 on deluxe memory foam that I cut up to size, only to discover I did it completely wrong and had the wrong foam type. To me, that was a $600 lesson on researching well before pulling the trigger. I just say that to make me feel better, though.