Regarding your brakes question, I'm in the process of doing this myslef. Seems that (for reasons unknown) the previous owner of my bike (a '76 F) replaced the rear disk brake with a drum instead. It works ok, so clearly, you can go back and forth. It still bugs the hell out of me, so I'm going to switch it back (the rust on the rim and that broken spoke I didn't notice is also helping the decision).
I've been reading old posts and checking with a few members around here. Take what I say with a grain of salt, since I haven't yet done this myslef. What it appears that you'll need to do (assuming the rear is the same as other bikes) is replace the rear wheel, swingarm, and brake stay with those off of an F series. You may need to fabricate something to correctly mount the brake pedal and master cylinder. I've been told also that the rear brake on a 75-76 was actually too strong and that the 77-78 model is a better choice. In my emailing with cycle salvage yards, it looks like it'll run ~$300 or so if you go that route. Taking your time and picking up the various parts from ebay or members (check the sale forum) should allow you to do it (?much?) cheaper.
Good luck, and if you get it to work, make sure to post your results so that others may bask in your glory. Welcome to the forum.
Dave
