I am sure that someone will know the answer however, I seem to recall the opening in the fuel tank for the pump to fit into has a pair of slots on each side. This would suggest the pump itself has a pair of lugs. So, if my memory is correct, it's a bit like a bayonet bulb and needs a twist. I am only going by memory and I AM NOT SURE. There is a new pump on eBay and the pic looks like it has the lugs I have described. Be careful - let us know how you get on. Steve
Edit: I think KC3 has done this job before