1990 Chassis cab motorhome but I can't seem to find any stamped in chassis number. Is there one?

It should be stamped into the floor between the edge of the right-hand seat (passenger seat if LHD) and the door opening, running alongside the seat frame from a point near where the handbrake cable goes through the floor.

There would originally have been a flap in the carpet, but as most have been replaced due to age and wear, it's not uncommon to have to lift the carpet and any other floor covering to find it.

Thanks RS3100. Mine is LHD and that RH side is particularly rusty. It's a problem here if the stamped numbers cannot be read on annual test.

Yes, they do have a habit of rusting out, and the stamping was never that heavily impressed either!