From the factory 2003+ 4Runner, 2005+ Tacoma and 2006+ FJ Cruiser have an extended breather for the front diff and transmission. They are located in the engine bay near the battery. So are you talking about using that "manifold"? It's not really a manifold but just two breathers joined.
FWIW, why do you think you need to extend the breather on the rear axle? Not saying you don't but the little breather on your axles is already designed to be a one-way valve to burp pressure and stay closed when the diff gets dunked in cold water. It works OK for occasional use. But the chance does exist for the spring to get weak or it to clog and not work. I replaced them after about 15 years on my 1991 (which had none extended from the factory) but the ones on my 2008 still seem to be working. I eventually extended the diff breathers on the 1991 using sintered metal pneumatic filters.
Extending the line comes with some things to watch, a kink in the hose can over pressurize the axle and force gear oil past the rear axle seals into your drums. It getting cut or pulled off will let dirt in unabated. I think that's why Toyota didn't put them on the rear axles, routing the hose and preventing it from being snagged was more effort than it was worth. The front diff and transmission (and t-case) don't move much, unlike the rear which twists around being a live axle.
Also you'll see the breather run up the fuel tank filler hose and into the space behind the gas cap door. People have found, at least on Tacomas, the breather eventually stops working. Whether that is due to fuel vapors or being bumped, not sure. But running it into the bed of the truck is actually preferred if you use the spring-loaded ones from Toyota.