Dana 44 axle swap Big vs Small Tube

[BrianG]

Hello, after hours of searching, I can't seem to find an answer to this question.

I have two Dana44 Axle assemblies. I'm trying to make one. The one that is under the truck which I am rebuilding is a smaller tube (older I believe) unit. I just replaced the ball joints and am half way through with the axle u-joints. I needed some parts off the other housing that I have so I tore it apart. Upon doing so, I realized that the axle shafts are much thicker in diameter on the one that is not under the truck. I also realized that the one out of the truck has bigger axle tubes. I believe the one that is out of the truck is around 76 or 77 and the one under the truck is possibly a 69. I am planning on using the hubs and spindles from the newer unit. ...... So, my big question is, can I, or should I use the heavier axles from the big tube dana 44 in my small tube dana 44 housing. The lengths seem the same, the splines all match up, only the thickness seems different. I've read and read about differences in the u-joints, but I have installed one already and it seemed to go in with not issue, so I think I'm good there.

Any and all help would be greatly appreciated.