No. They have a different input shaft that is 1" 10-spline and set in a different case than the early top center shift transmission with the 1 3/8" 10-spline.
I believe some of those gears and related parts from a '49 transmission will work in the earlier boxes. PM or email Mac Van Pelt. He could/would tell you for sure.
I would agree. Why tear that apart and only use some of the gears in an earlier transmission. If the '49 trans is good, it would be valuable for someone who needs that specific transmission. Gears for a '47 truck transmission would not be that difficult to find.