Looking back at the pics of your cabs, they seem just big enough to house the speaker with maybe an inch or two on either side. I seriously doubt if there is enough room to put up the extra wood I mentioned earlier, and as far as porting the cab goes, I think you need a certain amount of enclosure space to get the benefit from a ported cab.
Most cabs on the market are undersized for a single 12" speaker, but that's for the sake of portability. Your Peavey cab is probably a better candidate for porting or baffle bracing. One thing I can say about an open back cab with baffle bracing is that the bass response is there, but it's tighter than an open back with the speaker mounted on the baffle only. The ones without the bracing get flubby, or even a bit farty when you drive a lot of low end chunk into them.
If you're adventurous enough to build your own cabs, and select your own speakers, (depending on your power requirements), you could get what you're looking for. I would recommend no less than 1.5 cubic feet of enclosure space for 75W speaker or higher, and definitely reinforce the baffle. Even if you decide to port it, that kind of power will definitely rattle the baffle. The internal baffles like Richard is looking at, will work to help direct the air flow if you port it
I recall Genz-Benz made some really nice ported 2X12 and 4X12 cabs. I don't know if they made any 1X12's like that, but didn't ADA have something like that?