Hi there Chris
I know exactly wheree you're coming from about availability of parts for these (I had a '69 model for 4-5 yrs)
Might i suggest checking RT104 ('74-'78)/RT118 ('78-'81) for brake parts...
Engine parts are a bit more readily interchangable, the 2R is very similiar to the 12R used in most early Toyotas (Hilux, Hiace, Blizzard 4WD) to name a few........
Good luck with the upgrades & be sure to keep us posted with a 'Rides & Projects' thread..