The trouble w/ the IHC 5-speed OD, is when they made it an OD, they just replaced 4th w/ OD, and didn't change any other ratios, therefore there is a big gap from 3rd to direct. It didn't work when hauling a load, however, if you have a 2-speed rear in a big truck, it is OK.
I replaced the 5.38 gears in my K-5 w/ a Dana 70 w/ 3.73 gears and a direct 5-speed and it is much better. The 5.38 gears were so noisy, I was afraid to drive it too far from the house.
