If it were me and I wanted the caliber and stock configuration that you want, I would start with a blank with the barrel channel and ramrod hole drilled. I like a gun to fit me, it makes a world of difference compared to factory pre-carve offerings.
I wouldn't use a 7/8" barrel and would opt for a B weight swamped .45 barrel.
I have built two such guns, a Beck and a fowler turkey gun.
First, I bought a blank from Dunlap and had it sent to Fred Miller (Knob Mt now) to have the barrel inletted and ramrod hole drilled, he did a super job.
Next, I got a full-sized plan to use as a reference from TOW and traced a cardboard pattern to mark the pattern on my blank.
I made an adjustable try stock to determine the perfect length of pull and drop for me. After I got the measurements, I altered my cardboard pattern to accommodate them.
The full-sized plan showed cutouts of various places up and down the stock to give you a good idea of how to shape the wood. The plan apart from the side profile is just a reference and not an exact guide to follow as your parts may be different than the ones used in the plan.
Shaping a stock is not difficult at all, once the butt plate is on, it shows you how to proceed forward. I use a contour gage to make sure the wood is rounded correctly where it needs to be.
This is only my second gun build; I used the same method on my first gun but left too much wood on the stock that for a clunky looking gun, I got it right on this one.