I have two for consideration. Neither are exact but if you are Building the rifle, either could be made to work.
I don't see the Caliber you want, but here they are.
I have a Rice taper barrel in .58 cal. Breech is 1.055" and at 34" length it is .815". Straight Rifled. Flared Tang.
This barrel is 40" long but can very easily be cut & crowned. (Stamped Custom @ breech)
Also a Rice taper barrel in .45 cal. Breech is 7/"8 taper to .800" at 34" length. Round bottom rifled. 3" Straight tang.
This barrel is 42" long but can very easily be cut & crowned.
PM me if either is of interest.