I have a 2ton '46 Chevy that has been converted a little. The 2-speed has been disconnected from the vacuum system and bolted fast in the hi position. A brownie box was added with a bubba cut job attaching it to a shifting lever that's a little out of place.

OPTION #1 If I attached the vacuum system I would have to rebuild the vacuum system (I haven't looked to see what needs done) and remove the brownie box and buy a one piece drive axle. Also this would remove the clunky awkward shiftier handle making it so much nicer than it is.

OPTION #2 or leave the brownie box, and still need to rebuild the vacuum system but I may be able to push that back for a while. And then replace the handle to make it a little more user friendly.

My question is:

Is there any advantage to having a brownie box or 2-speed on the rear?
Disadvantages?

I'm assuming it would be redundant to have both hooked up at the same time and not run correctly.