I have one of those - for a few years it was a plain mower, then when i moved south i turned it into a 'stock mudder' - meaning it took a bath in the swamp everytime i visited the folks - it did pretty darn good for a stock tractor - only complaint was the stock rear tires didnt have a ton of traction .
Ive since dragged it down here and did a 'few ' mods- ive went back n forth about wether keeping it stock or making a mud/trail runner - so far im making it the latter.
Ive made a thread about it : http://atltf.forumotion.com/t146-agway-offroader-project
but heres a pic of it as it sits:
I welded some 3/4" bolts onto the ends of the spindles to fit the rear tires on the front - put some steering stops on the back side of the front axle - only real issue is the steering radius is dramatically reduced , has plenty of ground clearance tho and flex - itd probably work better if id bring either the stock axle lower down or swap it for a whole new one.
The rear wheels came off a larger tractor with a 3/4" keyed hubs ( stock type trans) - fronts came off another murray . I did swap pulleys - because the stock 3 speed was toooo slow , i just wanted a bit more speed then it originally had, not racing fast tho.
Front i think is a 4-5" and rear is a 6" (original was a 8-10") .
Im planning on using a 11HP briggs, eventually id like to make a rack for the back , maybe a brush guard for the front - and places to mount my winch.
For hard core offroad, youd want a sub chassis under the stock pan chassis - specially if youre gonna lift it at all .
I did notice in the pic of the transmission- one of the transmission brackets ( ubolt) is broken/loose. I had the same issue with mine- i just used an old muffler clamp.
For traction alot of people use ATV tires - id say those stock front tires would need to go ( i had those on mine- thing wouldnt turn hardly at all in the mud- replaced em with some turf tires) .
looking forward to updates.