There is a buyers guid on the RS500 out 1st October in Fast Ford which might help you. Chassis number (which is down by drivers seat & under bonnet) should be GBBE GG 38600 to 39099. Engine numbers should be YBD0015 to YBDO537, to be a genuine 500 also when ariel is up, press rear boot lock and the ariel will come down, wiring on the ariel is different than another Cosworth.