Registering in Vermont is a quick way to get them classified as a RV.
It might take a couple of weeks or so to get plates via mail, but that's likely your fastest way to get the buses registered without the hassles of going through a DMV inspection in PA?
Unfortunately, there might be added issues if you go that route.
Mainly because you're converting them to food trucks. There will likely be lots of red tape for you to clear before getting either of them "blessed" by any health dept. in any state.
At a minimum you'd have to go through a DMV inspection to get them changed from RV to foodie.
If I was in your shoes I'd cut one of them loose ASAP, as it's enough work to convert one vs trying to outfit two! (unless you can pay a shop or someone you fully trust, to do the conversion/up fitting on them).
Please don't take this the wrong way, I'm not attacking you for your decision: Hopefully you get some help quickly, as it doesn't sound like you researched what you're trying to do very well...
Good luck in your projects and business plans, going forward Viola...