There's a seat base [says DT1/RT1] on trademe number 763106555, might be worth a look. Pic two is clearer from underneath. If you're stuck i think i still have a couple of RT2/3 headlight ears up on trademe, not sure now if the RT1 are any different. Mine are pretty rough by memory. I also have an RT2 or 3 Tacho which is new but put it on my experimental [make that cock up] bike & these tachos were themselves a cock up that year as had no damping on the needle, hate vibration & are just horrible. I remember thinking exactly that when that year came out--[they've fkd up this time]. Got the tacho on my DT1 experimental bike with an RT1 crank which worked very well but just parked it up after proving a point [in an R5 frame for experimental purposes up n down our road but damn population's moving too close for what we used to do 50 years ago on my Matchy 500 with SH cams--sorry there i go again. Good luck with the resto & was just thinking the AG100 from say 1980 on had a similar looking seat to the RT1, just plastic base & bolt on type but is too damn hard [the grasshopper 100], square sided too [have a Agy myself.]. Make sure the one on trademe 'is' an RT1 not RT2 as were different. Lloyd thats selling it is a good guy & races a Cooper i think with my old RT2 motor with RT2MX top end on it. Too long ago now. Cheers.ps, my auction has an oil tank but can't find the light brackets auction o maybe i forgot to list them. Auction 760240168.