I recently bought a used Peavey Bandit in hopes that I can convert it into a multipurpose tool.  My other two amps are 8" combos, a Vox Pathfinder and a Randall RD1C.  Both have line and speaker outs, and the Randall has an effects loop as well.

I'm looking to do a couple of different things with the Bandit, but I'll focus on the first of those for now.

I'd like to use the Bandit as an speaker cabinet.  With the Bandit turned off, I'd like to simply connect the speaker outs of either of the other two amps to the 12" speaker in the Bandit.  What I'm envisioning is connecting the two wires coming out of the power amp and currently going to the speaker of the Bandit to some sort of switching jack into which I could connect the speaker out from either of the other two amps and then route back to the Bandit speaker.  The attached image shows the two wires to which I am referring.  I'd like to mount/attach this switching jack to the underside of the Bandit amplifier's chassis, preferably without having to drill into it.

So, how best to accomplish the goal of being able to connect a speaker cable from another amp to the speaker of the Bandit?

Being able to use the speaker in a combo as a speaker cabinet seems like a fairly common thing to want to do, but I'm just not sure what is the best way to go about doing this.

Thanks for your help,
Victor