The book you want is
The More Complete Cannoneer by M.C. Switlik. There are earlier addtions out there called
The Complete Cannoneer You don't want them as they are missing some important info.
I got mine from South Bend Repilcas
http://www.specialtymile.com/southbendreplicas/page1c.htm What you build is up to you. I like to build guns that look like the real thing. Others just want something to make noise.
Are you going to do the shop work yourself? That will have a bearing on what you make also.
Maybe all you want is to add a breech plug and trunnions and some sort of wheels. If so do it.
If I had your barrel I would be thinking Whitworth rifle or Parrot rifle. But then I have my own lathe.
Something to keep in mind. Your bore is 1.6 inches. If you build a full scale gun the bore is going to look small. Build a gun scaled to the bore and it will look big.
There is one obligation for getting advice here...you have to keep us advised and post pictures