You need a minimum of 50 posts before you are allowed to sell anything and you have to post them in the correct section, which is conveniently called Land Rovers for sale and Land Rover accessories and parts, the name should give a bit of a clue...

A knackered starter motor will often spin with no load but not develop enough torque to turn the engine over.

Something like this? https://www.johncraddockltd.co.uk/gts004-single-half-tow-step-black-finish.html

This is the one I have on mine. I know it is not strictly a Series 3 step but I think it looks ok and it acts as a useful rear bumper.

You need to have made at least 50 posts on the forums before you can advertise your vehicle for sale. @blue beasty may be along to have a word soon.