Fuelsafe makes a fuel cell that will bolt into the FFR, its ungodly expensive though.
http://fuelsafe.com/store/fuel-cells...ve/sm122a.html

Or another option is to do a trunk fill (no side fill)
http://www.harmonracingcells.com/sto...-_CURB22B.html

Make sure the fuel cells have a collector/surge tank box in it with the fuel pump, that will eliminate fuel starvation.