Here's the problems as I see them. I think the doors will fit as far a dimensions go. But the styles are different. 51-53 doors have a crease (body line) (?) that runs about midway through the door. It follows the fender line. With the 48-50 doors, the crease or body line does not extend as far. So they look different, though you may not catch that at first.
Also, if you remove the vent window you now have a gap that will have to be filled somehow where the window post used to be.
The other concern, and I don't have a way to check this, but you have both versions of doors so you can do this, I suspect that the window regulator is mounted in a different location to compensate for the vent window. It might even be a different window regulator and mechanism.
so these are some things you may want to check out. I have vent windows in my doors and thought of pulling them out. After I looked at all the work involved I decided I was going to either keep them, or find replacement doors. I decided to keep them, in other words, I chickened out on that project.
OK, it's New Years day and I have too much time on my hands. Here's two pictures that I hope will show the difference between the body lines on the doors. Notice the body line on the '53 stops mid way into the door, on the '48 it goes almost to the end. hope this helps.