The modern frames and barrels are completely interchangeable. I don't know about the early guns but there is currently NO physical difference between handgun and rifle frames, they are one and the same. As far as I know, that's been the case for decades. There was a lawsuit between ATF and T/C regarding this in 1992, so it's been a LOOONG time.
ATF has, thankfully, backed off on their ridiculous opinions on this matter but not until last year.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.