20w-50 oil as Randall says. As for parts,I use either the Roadster Factory or Moss. Is your oil filter the original type or the replaceable spin-on filter (a conversion)? If it's a spin-on, almost any parts store - Auto-Zone, etc. probably has a cartridge to fit. Some owners are sticklers for authenticity - I'm not one. Be sure to check the coolant as RI gets cold in the winter and if your car came from down south, the anti-freeze may be insufficient - if there even is any. As for plugs, owners use Champions, Bosch, NGK, whatever. Go online and spend some evenings looking up questions.Almost every question you might have has probably been answered - usually by someone on this board. Good luck and enjoy your TR6.
Paul, from nearby CT.