Rad, have you got a copy of Practical Junk Rig yet? You're going to need it as a reference for all the rigging, but in the immediate future, it will talk you through the process of designing the sailplan, in detail, and getting the balance right. It's available from Amazon, and also on eBay for £34.
And Chapter 16 describes various examples of junk rigged boats. In particular, there's "Design SSF/1" (designed by Blondie Hasler, but not actually built). It's based on a Scottish Fifie, which is a plumb-ended 50ft fishing boat not dissimilar to yours.
The rig is a junk ketch, with the mainmast well forward, carrying 1020 sq ft, and the mizzen mast just about where your deckhouse is, carrying 510 sq ft. The mainmast was planned to be lowered.
This placing of the mizzen may not be convenient, but at least it confirms the total sail area needed as being in the region of 1500 sq ft.
A crab winch was intended to be used for the main halyard, and I would certainly want a reel winch with a brake to handle such a large, heavy sail.