Ben there done that.
Start with a pisol frame(mine was a 7-08and I added a 223 fer prairie dogs) and add a stock and long barrel,barrels of your choice.
Remember to take the stock off before you mount a pistol barrel as Mr Law REALLY frowns on short barrels with rifle stocks!!
I found my 15" 454Casual barrel stayed on the TC frame
and I shot 45lc out of it,prefering my 1300Win for shotgun work and a Ruger VT223,Old Ruger tag with an 8twist 22-250,ColtAR, Savage204,223,243,25-06,605-284,30-06 for varmints.
I sold the all the barrels save the Casual but kept the
stock,someday I'll add a smokepole?
Found out I aint a one gun type of guy and even if I was it would be an auto

It didnt work fer me but may be just what you need,give it a try but start with the pistol!!!