Hi, I am also working on a project 1980 tf 185 and I was having trouble with the electrics. I did not have a regulator and part of my loom was missing and I did not have a battery so I just ditched all the dash lights and the indicators etc and I am just running a non sealed beam headlight with no regulator it works fine as long as you dont start the bike with the light switched on because the voltage and current fluctuation will blow the bulb

let me know how you get on with it