For the vehicle mode the minicons leader-1, Clench and blackout
imo blackout best represents the g1 toy,with his knob like hands and wheels on the side of his leg in bot mode, you can mod the toy by removing a wheel of the same toy and placing it on the one toy so it looks like he has three wheels
another good representation is X-Dimension Move MM-14 (best 1 in imo)

this leader-1 repaints looks accurate or Calburn
Black Megatron w/ Barrel (Black) (Ultra, 2003)
A contest prize limited to 100 pieces, Megatron and Leader-1 were redecoed in primarily black with dark purples, grays and olive-greens. The contest was listed in the June 2003 issue of Tele-V Magazine in Japan.
Wanted items:
eHobby Orion Pax and Dion