in '74 & '75 the t-34, t-35 & t-36 5-speed manuals were updated and coded as t-494, t-495 & t-496 (13494, 13495 & 13496), all factory available. The t-494 was od in fifth. The t-495 & t-496 were direct in fifth. They all have a pto opening on both sides of the trans. The newer models now have synchronized 1st gear. The difference between the t-495 & t-496 is that one has a deeper 1st gear then the other. I have the gear ratios somewhere, but I can't find them now.
The "one ton" trucks in '74 & '75 did not get the designation of '300' they were model 200, same model number as the 3/4 ton.
The all wheel drive (4x4) one ton 200's did not have the set back engine, wider springs, etc. Like the 1/2 ton 150 & 3/4 ton 200 did.
They are essentially the same as the '73 model 1310 4x4.
Your rear alxe should be a Dana 70 if it is a single wheel model, or an IH ra-15 if it is a dual wheel model.
10,000 gvw was the maximum for the 200 one ton in '74 & '75, possibly the highest for previous years also.
You May notice that your engine is drilled & tapped for the side mounts as used in the 150's & 200's set back models, but it is mounted with the front horseshoe mount. Also your front frame rails are clearanced slightly for exhaust manifold clearance.