If I were to remove the solenoid from a 1949 starter, could the "mechanical contact/linkage" from a 48 starter be installed on the 49 starter and would it work on a 48? In other words, I have a nice 49 starter. What do I need to do to install it in a 48. Everything is stock. Thanks.

Yes, providing the 1949 starter has the necessary holes on top for nounting the switch, etc. The drive housing from the 1948 would need to be used.