You have discovered the same issue most ‘AD ‘bolters run across. The bar when originally designed in 47, ran nicely in the channel below the handle, with the handle facing up, so the bar didn’t interfere with the interior door panel. You would open the door by pushing forward on the handle. In ‘49 they changed the direction the handle faced. One of GM engineers quick fixes. I suppose handles that opened on the forward position resulted in doors opening in crashes, are not such a good idea. They installed foam blocks to push the cardboard panel away from the inner door to allow more clearance for the bar. Much cheaper than changing the design of the inner door sheet metal to accommodate the bar in the upper position. It does cause the cardboard insert to bulge out a bit, but I suppose in a truck, that was acceptable.
I struggled with that same issue, seeing the nice depressed area where the bar sits so nicely, I tried to get it to fit but with no success. Unfortunately, I don’t have the answer and searched for answers, both in this forum and on the web without a suitable resolution. The only straight forward way is see is to change out the regulators to electric. Costly and not original. At least you know what the issue really is.
Maybe some other ‘bolters have other ideas they can share.
