wow.. i could have sworn that said a later ford year not a 64.
64 would have NOT been lucas.. that was 65+ guess this small screen is playing with my eyes.
do this.. pull vreg field line, and slip belt off genny.
jumper bat hot to field and armature at genny. if it motors.. the genny is likely good.
slip belt on, start up.. get to mid throttle.. jump armature to field.. amps come up? if so.. replace the reg... though sure won't hurt to pry the can open for a looksee. might see a dead bug inthe contacts.. or carbon on them.. worth a look, even if just to see what one looks like.. etc..
sorry about the prev post. I thought you indicated a 3 cyl 2000 from year age.. not the older 4