Atlantic Coastal Welding (Speedytanks) links to the following:
http://www.marinesurvey.com/yacht/fueltank.htm
which should be a good start. Sunshine Marine, Boyd Welding, CL Mattson, Best Fabricators, Ezell Industries and RDS websites might have some good information as well.

There is a previous thread on this forum about cutting the tabbing part way up and through-bolting new L-brackets in, but of course, the existing L's that you cut off could be glassed back in.

GL,

-Chris