With the cost of today's parts and labor even if you have a place to work and are physically able to get to and fix every part on the old van you still will spend a lot more than you think. As HDR says rebuilding from front to back means every thing worn gets fixed or replaced, no cobbling to get by, OEM new which is a lot of time and money. I just looked at a 1966, 8 lug , overdrive automatic, 350 cubic inch V8, dual optima batteries, power brakes, power steering, new glass, new hinges and door hardware new paint and new flat bed with side tool boxes, painless wiring harness, aluminum radiator with dual electric fans and AC two wheel drive pickup. Owner had spent over $16,000 in parts to make everything new and updated so he could haul a load and cruse at 70 MPH on interstate. He had had it 2 years and put 16,000 miles on it. He would go no lower than $8,000. I'm still trying to figure out why I haven't bought it but after restoring hundreds of vehicles I can tell you there always seems like there is something that you missed fixing unless you start with a frame. I think reliable vehicles are made after a lot of researching of common problems and doing a preventative intervention to keep them that way or at least something the owner can deal with no matter what the vehicle is.
