Do they need reprogrammed, or can I strap two of these together stock and charge on the cheap?
There are literally thousands of CC-CV power supplies you could strap together and charge on the cheap.
Making them fit the tank area neatly with a nice cover and not overheating is harder. Making it work with J1772 properly also takes a little effort.
Overall if you can do it depends on your skill level. I hate to use a cliche, but its one of those things where "if you have to ask, you probably shouldn't be doing it."
You would be going into an uncharted area where there are no how-to threads on it. You're on your own. To some that sounds fun, to others, terrifying.
If you want to build a cheap charger, I would stick to a couple stacked meanwells.
If you want to built a tiny, powerful charger and keep it cheap, you need a little EE-education and build a CC-CV buck charger...
If you want it smaller than the stacked meanwells, and cant design it yourself, you're stuck with the diginow charger as your next choice. Its still much cheaper than anything comparable.
next choice after that is the charge tank.