I have swapped calibers with 38 Super and 9mm by changing out the slide and barrel assy, the same ejector works. The 9mm will feed fine in a 38 Super magazine, not vice-versa.
I have mounted a nine on a 45 frame and had feeding problems, as the ramp on the frame is different, and the deeper cut on the 45 ramp can present an edge at the bottom of the barrel's throat that can hang up the bullet nose of a nine or 38 Super unless it is a roundnose or conical.
If you swap slide assemblys, open and slowly cycle the slide (no ammo) looking to check the feed ramp alignment to see whether the frame's ramp and the barrel's ramp mate up smoothly. Adjustments could be made to make it reliable.