I think the 75s had a Dana 44 with a unit hub, if the truck was a full-time 4x4, which was common for mid 70s Dodge. They also used a small 4.5 X 5 lug pattern. If you keep the tires in the stock size range, you shouldn't have a problem. Go bigger or get crazy on the go pedal and you'll be replacing parts. Fortunately Dana axles are common and have huge aftermarket support. Ideally, it would be better to swap to a Dana 60, after all, they are bigger overall and that means generally more strength. However they can be harder to find and cost a bit more to purchase than another 44. In the absence of a Dana 60, you can upgrade a Dana 44. It won't be cheap. It could even be more expensive to upgrade the 44 than replace it with a 60, but if theres a serious lack of 60s in your area, this maybe your best option. If you choose to upgrade, everything internal should be replaced with high quality parts and high strength parts if available. Stronger chrome moly shafts with a slight diameter increase, are available. Stronger u-joints also exist and these greatly increase durability of the guts. Aftermarket ring and pinions can also improve durability. Externally, you should consider a knuckle-out swap to get rid of the unit hubs and the smallish lug pattern. You can use a newer 5.5 X 5 pattern out of a newer 80s Dodge or Ford (Though you'll have to use the Ford brake caliper) or an 8 lug pattern off of a Dana 44HD, which gives you three extra lugs and slightly larger brakes. Best of all, any of these options will allow you to run lock out hubs. You should consider addressing the rear as well. It's usually not much stronger than the front Dana 44. If you change the front lug pattern, it's easy to swap axle shafts. The 5.5 X 5 lug pattern was common on later models of Dodge truck using the same axles and should swap. Dana 60 rears are easier to find than fronts, so if you do the knuckle-out swap using 8 lug hubs and rotors, a rear Dana 60 would be an ideal compliment, as they will both use the 8 lug pattern.Got a new question got 75 dodge w100 with Dana 44's up front and 8 1/4 rear end (3.55's)
Will dana 44 and 8 1/4 survive on a 4bt?
Myself I would not want a Dana60 with tires under 39". Due to their shear size you lose too much ground clearance!Bouncing or high horsepower then no D60+ for that type of abuse
Regular driving and mild wheeling D44 is perfectly adequate
A built D44 IS cheaper than rebuilding a stock D60 (if you account for cost of axle difference) stock Dana60 parts are ridiculously expensive
Many folks will scream at you that you NEED a Dana 60. By far most rigs do not need one. The more folks that seek D60 for their rigs (that may or may not need one) the more expensive they are for the Hardcore guys on 39's