I would think a junk yard high top would be ideal for your budget setup. Lots of people like the idea of the pop top. However, reality is often does not match up. Pop tops have their place, and they can be great, but a pop top can be windy and wet, as well as loud. There is a mechanism to break/wear, and depending on the top design you loose some of your roof storage (or maximum weight).
The high top is always there, so there is no shuffling gear around and popping the top every time you stop. They are dry, quiet, and can be easily insulated. Adding a powered roof vent does amazing things for comfort in hot weather.
High tops often don't have a large impact on fuel economy either. You do need to deal with the extra height, but that has been easy to adapt too in my experience. Being able to stand up inside your van can be priceless. :victory:
I see lots of E series accessibility vans with high tops. Some government ones as well. Many are about the right age to be ending up in junkyards or on craigslist. Installing the top could be lots of time (Depending on design). Thankfully sikaflex 252 and fiberglass mat can fix just about anything.