problem is finding a manual transmission, or dealing with the auto-tranny challanges.
There are a number of minivans that were originally equipped with manual transmissions, including both the first and second generation Chryslers, Ford Aerostar, Toyota Previa, as well as both the Toyota and Mitsubishi mini box vans- which are actually collectible now.
Swapping a manual into any of these models is pretty straightforward. The transmissions, shifters, clutch pedals and so forth are typically also shared with other models, so while there may not have been a ton of minivans with manuals, its not very difficult to source this stuff salvage with an interchange manual. Its also nice to do a conversion this way, because you can keep the vehicle in service with the ICE/auto until the new, complete drivetrain is ready to install.
Of these minivans, I've looked the most carefully at the Aerostar, because:
1. They are very durable, with a hybrid welded unibody/frame rail chassis widely known by the cargo truck crowd as toughest of all the small van chassis.
2. They are larger than most minivans, with a stock GVWR up to 5300lbs, that you can actually build to and not have it wear out and warp apart over time.
3. RWD makes for a simpler conversion, and its what you want if you start putting packs in the middle and rear of the chassis.
4. Surprisingly aero, if you block off the grill, which is also pretty easy to do on this model.
5. Still out there, and cheap, too, especially if they don't run right.
Just a thought...
TomA