can i run and a/b box through my effects loop to switch between the sound of my pedalboard going through the loop and the pedalbaord going through the amps input?
Oh, but I believe it is possible.

It would just be an enormous pain in the ass, and pointless to boot.
Not to mention most likely noisy as hell...

You'd need a 6pDt switch, or two 3pDt's that you can stomp at the same time.
Gimme a sec I'll rig up a diagram...
Signal path goes like this:
I can only imagine what crazy-ass ground loops you'll get, but the signal would make it.

hold on...

I thought the question was can TS run his mfx through both his loop and frontend jack and switch between the two via an A/B switch in his loop.

...aaand I know that makes no sense. not like things always make sense around here... I'll try re-reading after pounding down a few more cups of coffee...