Just did my 74 TCS rear bearings. From a mechanical stand point I would think an open bearing could be used on the inner as there is a lip seal there, but I would see no advantage to use an open bearing, other than maybe increased the amount of bearing grease? The outer bearing is another issue as there are no provisions for separate seals. My hubs are open at the bottom (3/8" hole) so dust, dirt and water can migrate into the cavity and get to the bearings. Thought of placing a zerk fitting there, filling the hub cavity with grease and then using open bearings on the inside, but as much as the car is driven not worth the trouble and why reinvent the wheel. I used all sealed bearings and the rear inner seal. It will keep out debris in the cavity between the axle and trailing arm. Just packed it with grease for some seal lubrication. As a side note the new sealed bearings I purchased all were lacking in the amount of grease. You might want to check the amount of grease in your new bearings before you install?
