VeeeCeee,

Shes A Very pretty Green smile.

Definately the incorrect engine for M5 S1...I would Also have expected CAC or CAE, before the serial, but it is what it is smile I would like to see the stamping style in a clearer image for my own reference though, just to make 100% sure its not of the early style, which would make it earlier in the M5 Series (but still incorrect for your base)

The fact it starts with C generally indicates a very late or intersecting S3, Or model 8 serial. In any case it's another number in the mess of the S3 range, which is many and all but indeciferable.

Correct Range of 160,000- approx to 300,000+ would be accurate.

All Model 4 and 5 Autos and specials used the same colour on both base cowl and handle bar retainers. Galmet Avocado.
Handle bars and bracket both Victa Green (Wattle killrust in Deep Brunswick Green). This is of course excluding dept store models.

The colour choice however is entirely your own:) Orange is nice lols...

Linish your exhaust flange with a small degree of outer taper will help it seal better, and dont overtighten.

Anyways,Do it how you want Mate, as long as your enjoying your Saturday Fun! smile