I have a '68 Bandmaster Reverb (which is essentially a Vibrolux with a mid control) that I have turned into a 1x12 combo, and a friend of mine has a '69 Vibrolux, bought off ebay already converted to a 1x12 with a Weber P12N, and we both think that they are absolutely fantastic amps as 1x12s. For me, I would go so far as to say that it is the perfect Fender amp - perfect size/weight and wattage, good to go in any situation, with any drummer.
Initially, I tried a bunch of different 8ohm speakers, because they are readily available, and came to the conclusion that the amp's 4ohm output paired with 8ohm speakers just attenuates a little too much high and low end for my ears - I am looking for bright and twangy with a big bottom end, and that combination is just too mid-oriented for me. I bought an Eminence GA-SC64 for my DRRI and felt it was the best vintage-styled speaker for a Fender that I had ever heard, so I special ordered a 4ohm one from Eminence for my Bandmaster combo, and I am now totally set as far as Fender tones go - I even traded my DRRI for an AC30 as a result.
There are a lot of guys on here that will nay-say, and tell you that you are stupid for considering that 1x12 mod, and that two tens in a Vibrolux is is God's own choice for an amplifier and such, but I grew up a Eddie Van Halen devotee, so I am also very much a hot-rodder by nature (that wild young kid throwing humbuckers in a Strat utterly changed the world) and have no hesitation whatsoever to mod things when chasing the tones I am after. Now, that is with one caveat - I don't hack up or irrevocably mod any vintage gear - but other than that, I say go for it. Changing out a baffle is no big deal and easily reversed, and it might just prove to be what you are looking for. It certainly worked for me and my buddy, and I highly recommend it!