Stuff you need to know if you are looking to replace your booster:
I have seen 4 different boosters fitted to SW20's as OEM.
 
The 'fat' body boosters on early model JDM cars, (don't know much about those) and 3 other different 'thin' body boosters that have the same size body.
 
With the 3 thin body boosters the only visible difference was that the ADM '90-91 thin body booster had the vacuum valve mounted on the booster.
The '92 - '94 booster and the post '94 booster just have a pipe outlet (no valve) and they both look identical.  (With these the valve is mounted in the engine bay)
However, all 3 thin body boosters must have different internals even though the body size is the same, because the power in each case is different with the later model one the most powerful.
I don't know how Toyota achieved that.
 

I've been going through the part numbers and yes there are 4 different boosters from 90-97.
I still haven't found the specs for each.
 I believe there are only 2 ways to vary the power of a booster. 1) diameter of the diaphragm
and 2) the number of diaphragms.
So, it is possible that even in the same housing, the outer "clamped" edge of the diaphragm could be reduced thereby increasing the swept area of the diaphragm. Or they fit another diaphragm in the housing.... or....multiple things were changed to ....
re the check valve location - I don't think it matters. If I use one of the boosters without a check valve, I would install the check valve near the booster .

Actually moving the valve to the engine bay would add extra vacuum and compensate for reducing the tank ("thinner").  I wonder why they went thinner, when you read about people adding extra tanks to increase the amount of vacuum. (volume not pressure).