Hi Andy,
Iv'e built a fuel tank for my MX5 build out of ally with swirl pot and flange for MX5 sender. I have kept it within the dimensions of the SSC back end and the book. If interested it's on my Photobucket and if you like I can draw it up this weekend and send it to you on Autocad (I believe you have Inventor?) I've got it roughly drawn but without the flange...
The fuel tank we have made uses the sender/fuel pump without any mods but does slightly go over the diff plates.
Just let me know if this is of any use.... Johno
http://i1199.photobucket.com/albums/...0122011297.jpg