Vladislav

No, that's a different swich. That one switches main engine air intake. From normal way through the cap of the filter canister to from under the hood area via that second pipe at the canister. For cold weather operation as it is subscribed somewhere (in the truck?) and that seems as a Canadian thingy.
So that second pipe on (that Canadian style) filter housing is NOT for the tip turbine. This way the scoop in the hood works its role.
Asking the original question. No, Maxidyne tip turbine was way far from not the only engine option used on R's/RD's. Plenty of different Mack engines installed during 4 decades of production starting from Thermodyne gassers and ending with Mack 4 valve E6 and E7 (in the restyled RD's). Also engines of different brends could be used including such exotic as two stroke Detroit Diesels and Chrysler gas V8's. 
And if you want to learn as much as possible on your Mack truck the best (and the only?) way is reading this forum!  Personally tested

Yes, wondering and figuring is the way to new. If the mankind were only duplicating we would still use wariations of stones, not trucks, smartphones etc.
One more aspect floated up in my mind when I typed the above yesterday was the angle the hood sides go from the cowl to the nose. The cowl width is the same and the nose area is too probably equal wide between R600 and R700. If so the angle between hood sides of R700 is sharper. And if you add extension at the cowl its sides should be parallel, not the same surface as the R600 hood side. I just didn't type that originally, there was enogh for that post.  

RW II's

Guy, that's great news
Happily I can't go to that yard and start talking that thing out to grab it . Just kidding
Mack EP engine is a common Thermodyne overhead valves gasser.
If the memory serves it's 672. With updraft carburator and single ignition system. 160hp.
Generally the same as EY in Mack MN or NO but 672 instead of 707 and has standart oil pan (NM has a modified one to clear up a front drive axle)
Not many (if any?) restored LMSW's have original engine.

Hi!
I was surprized too much while looking the stuff you posted.
I'm shure 100% you have a deal with WW2 army Mack model NR of about 1944-45.
Would tell you more if I see a better pic of the chassis number. But we can read NR in front of it and it makes sence.
Frame and the bogie look original, front axle, cab and the engine are aftermarket.
There was Lanova in it years back.
Front axle beam is different from a factory one with budds instead of original spokes.
Fuel tanks, running boards arrangement and the gear box are definitely of NR.
Congrats on the save.
Vlad.