what you can do is get a separate swirl pot such as the one fitted to post-84 cabrio and scirocco plus all g40 shape polo or something aftermarket. fit an inline main pump such as a standard mk1 gti unit, or whatever you fancy aftermarket with the right spec, then make up a bracket to mount tit all plus filter and accumulator under the car. as you say the mk3 fuel pump is no good to you, though people have modified them to accept the MK2 kjet style pump inside. the main thing is fab up a good threaded fitting on the top. then all you would need under the car is the accumulator and filter you can buy aluminium fuel pump housings which fit same as original, but those understandably are expensive
You need to work out what fittings you need really but here's the link. https://www.ebay.co.uk/itm/35276009...sWD8xfEQxDmg6ouLzQdm-GXjckKbRnUxoCH_EQAvD_BwE
