According the the 1976 Ford Data book, the Dana 44-1F in the Bronco has a 2.75 in. diameter tube, 0.312-in (5/16") wall thickness. It was rated for 3,000-lbs. GAWR. The '71 & '74 Data Books are the same.
The 1/2 and 3/4-ton D44 axles are listed with the same diameter but 0.50-in wall thickness. GAWR was 3300 and 3550 respectively.
Going back to the D30, the '66, '67 & '68 Data Books list it at 2.50-in dia. and 0.312-in wall thickness.
In that same era, the half tons were 2.75-in. but only .375-in. wall (3/8-in.) The D44HD (for the heavier GVW 3/4-tons, optional for the lower rated trucks) was 0.50-in wall.