I looked at SR, they have a 36 lb/in max and a 20 to 100 oz/in, so if you need closer to 50 lb/in, they won't work.
I know nothing about the Mountz, cannot help you. I do think for that low of a torque, the regular torque wrench design is not very functional, I think a torque screwdriver would be much better and more accurate.
Just offering alternatives here.
Seekonk (very good quality stuff) makes this vertical torque gauge (screwdriver with big disc and pointer to indicate torque. Many different scales. They also have a much fancier 3 to 30 lb/in adjustable slip type tool, again, probably too low a range.
http://www.seekonk.com/torqstart.html
GS-170 * 0-170 in. gr. 10 in. gr. 8 ozs. 8" $104.15
GS-350* 0-350 in. gr. 25 in. gr. 8 ozs. 8" $104.15
S0-12 * 0-12 in. ozs. .50 in. ozs. 8 ozs. 8" $104.15
S0-24 * 0-24 in. ozs. 1 in. ozs. 8 ozs. 8" $104.15
S0-3 * 0-3 in. ozs .25 in. ozs 8 ozs. 8" $104.15
S0-48 * 0-48 in. ozs. 2 in. ozs. 8 ozs. 8" $104.15
S0-6 * 0-6 in. ozs. .50 in. ozs 8 ozs. 8" $104.15
S0-96 * 0-96 in. ozs. 4 in. ozs. 10 ozs. 8" $104.15
SL-100 Left 0-100 in. lbs 5 in. lbs. 16 ozs. 12" $127.15
SL-100 Right 0-100 in. lbs 5 in. lbs. 16 ozs. 12" $127.15
SL-12 * 0-12 in. lbs .50 in. lbs. 10 ozs. 8" $104.15
SL-25 Left 0-25 in. lbs 1 in. lbs. 13 ozs. 10" $113.15
SL-25 Right 0-25 in. lbs. 1 in. lbs. 13 ozs. 10" $113.15
SL-50 Left 0-50 in. lbs 2 in. lbs 13 ozs. 10" $113.15
SL-50 Right 0-50 in. lbs 2 in. lbs. 13 ozs. 10" $113.15
SL-6 * 0-6 in. lbs. .25 in. lbs 10 ozs. 8" $104.15
SL-80 Left 0-80 in. lbs 5 in. lbs. 16 ozs. 12" $127.15
SL-80 Right 0-80 in. lbs 5 in. lbs. 16 ozs. 12" $127.15
You might also look at the Precision Instruments torque drivers. I think they make good tools, being in business since 1938. Kinda pricey however.
http://www.torqwrench.com/tools/drivers.php
1/4" Drive Dial Driver
– Drive Size: 1/4"
– Drive Type: Fixed drive
– Capacity: 10-50 lb.in.
– Increments: 1 lb.in.
– Price: $ 250.00
Specifications
Square Drive Size: 1/4"
Handle Height: 6-27/64"
Overall Height: 8-7/64"
Width: 2-9/32"
Weight: 1.00 lbs.
(w/plastic case): 1.65 lbs.
Finish: Nickel / Chrome
Meets or Exceeds the following Specifications:
GGG-W-686C, ANSI B107.14M
Charles