Can anybody tell me what the ohm rating for my 67' bandmaster(no reverb) is? Also, what is the difference in the output of the speaker and extension speaker outputs?

Probably 4 Ohm, but check out http://www.ampwares.com/ffg/ for a load of info on your exact amp. I doubt there is any difference between the speaker / extension speaker outputs (i.e. they are connected to each other) but if you find the appropriate schematic via the above site you can confirm that.

thanks!