First of all, glad to see more Mopar A-bodies in Lemons! You rocking the slant six, or does it have a V8? Shoot me a forum email if you want more advice than you could ever ask for. These things can be made to handle surprisingly well, and the judges will give you some budget leeway because of what it is. If you haven't already emailed Judge Phil with pictures, I'd do that. He'll probably tell you to go nuts.
If you're looking at running 13s/14s, I assume the car is still small bolt pattern (5x4"), right? If that's the case, you probably still have 4-wheel drums. If that's the case, I would say don't waste your time with 190TW tires until you at least have a disc brake conversion on that thing.
A quick search on TireRack shows a few options in the 400-500 TW range for 14s, and precisely one option (Kumho Solus, 700TW) for 185-70-13s. Unfortunately, the 4.5" width of those stock Mopar wheels are going to limit you to something like 195 max section width.
There may be some small bolt pattern 15" unicorn wheels out there, but in general any wheel in a good size for tire choices is going to require changing your bolt pattern to 5x4.5". Luckily if you want cheap and effective front discs, that's going to happen anyway. I won't hijack your entire thread, but if you want details on any of this just send me an email.
EDIT: To clarify, 190TW is not required, it's just the minimum. You can go higher than that, and for most Class C cars you probably should just to avoid throwing money away.
