Congratulations on your .45, now it is time to purchase a complete Glock 20 upper, so you can have a 10 & 45
I mean, that’s the easiest way to swap. But don’t you just need barrel and magazines (I have G20 mags already)?
And yes, I got a 21 half because it allows me a 20. And Glock designed it as the 20 and converted it to .45. Rather than most other guys who took a .45 and converted it to a much hotter 10mm.