Oh man, I just spent 10 mins or so writing my reply and then I realized im on crack and was talking about the completely wrong thing.
But I'll attach it at the bottom as its good tech for someone in the future to search for..
tonkota-
You don't want to use the R150F 3.0 or 3.4 V6 transmission because not only is its' bellhousing made for the bolt pattern of the VZ-family block, it is designed for the chain drive t/case (undesired) and will require an additional adapter and coupler just to convert it back to your gear drive t/case (desired). You could use the chain drive tcase if you got a tranny & t/case from a 3.0 V6 since it's a passenger-side front output, but since its only a 3 piece, the low range section can not be separated and therefore it can not be converted into a multiple reduction unit, and since it uses a planetary gear set to make the reduction for low range, no gear sets are available to lower the gearing as planetary gear sets become extremely weak as the size of the planet gears are reduced in order to achieve a lower reducing ratio. The only advantage with the chain drive is that it is a bit lighter (about 10 lbs) and can be shifted on the fly up to around 50 MPH where as the gear drive must be below about 5mph in order to shift it.
About the bellhousing, it is possible to use the R150F transmission behind your R-family engine, but you will need to convert it to the bellhousing of the R151F. Read on.
With all of that said, if you want to take advantage of the much stronger R-series transmission, then please seek a R151F transmission from a Turbo 22R-TE '86-'87), which as you may have guessed, is the same R-family block as your 22R-E, so the bellhousing bolts straight up, and the best part is that it is designed to use a 23-spline version of the same gear drive t/case that is in your truck right now. So all you would have to do is swap in a 23-spline input gear into your stock 21-spline tcase and you can directly install a R151F transmission.
Man if you can find R150F's cheaper then W56's then by all means buy it! In fact buy 5 of them and then sell them to us who can't get them that cheap!!
I would say that the average going price for a used W56 is $50-$100
Average going price for a used R150F (V6) is $200-$300
Average going price for a used R151F (Turbo) is $500+
If you can buy the trans for that price or less then its a great deal... I think you are getting ripped off with the W56's in your area.
I just checked
http://www.car-part.com and here's what I got:
R151F price range: $950 (Englewood, CO) - $400 (Traverse City, MI)
R150F price range: $1000 (Easley, SC) - $145 (Rustburg, VA)
W56 price range: $993 (Albany, GA) - $100 (Oak Ridge, TN)
Wow those prices are really high and then the low ball prices are what I expected except that the R150F really is a bit cheaper than I thought... A guy just came in recently who got a used W56 for a core for Marlin for just $60 from Sacratomato, CA, so I know the cheap ones are out there you just gotta look.
Well I've gotta get going and Ive sidetracked this enough so just reply back with what ya think-
Thanks
BigMike
This is my reply on crack. Sorry I was on a completely different track, but I'll leave this here for tech reference. So just disregard the following:tonkota, this is an awesome idea and once you build your custom R-family block to W/G-family transmission, then you could get a patent and mass produce them. :biggrin:
Actually the W- and the G-series have the same front housing > bellhousing bolt pattern, but this is a smaller pattern then the R-series front housing > bellhousing pattern, so you can not place a R-series trans behind a W- or G-series bellhousing. The only other 4WD bellhousing that Toyota makes (not including the new 6-speed 4WD trans) is the L43 4-speed which is completely different.
Making custom bellhousings is becoming more common these days, and I know of one Randy B who modified a R151F bellhousing to fit behind his Isuzu Amigo engine back in like '97 or so...
The R150F are cheaper and more plentiful. (than a W56)
What?! 
Where do you live? I'll fly a plane there tomorrow and buy everyone you can find if they are cheaper than a W56!! and Im not kidding! You aught to jump on 5 or 6 of them and then sell them on ebay! 
I would say an good price to pay for a used W56 is about $50-$100.
a used R150F (V6): about $200-$300.
a used R151F (Turbo): around $500 for some reason.
Can it be done? Is it a good swap?
Apart from a custom bellhousing, you will also need to change the input in your '85 t/case (21-spline) to a R151F t/case input (23-spline).
If you buy a R151F and make a custom bellhousing: Just swap out the input to a 23-spline Turbo Input and your ready to install the trans.
If you buy a R150F and make a custom bellhousing: Not only will you need the 23-spline input, but since the R150F is from a V6 that uses a chain drive t/case, the bolt pattern on the tail housing of the transmission and the trans to t/case coupler are not compatible with the gear drive t/case in your '85. This is ok as we make a conversion kit for all V6 owners and in this case you would just simply need our adapter p/n# 30-4GT if the R150F is from a '88-95 3.0 V6 or p/n# 34-4GT if the R150F is from a '96+ 3.4 V6. The cost of either kit is $349, so now you are above the price of just seeking out a R151F (a bit more pricey) to begin with.
