Wow! Super nice find. Congratulations! Heart and want is for sure with E55 but the fuel tank issue worries me most. I had the chance of a nice E55 too but like you hesitated looking at all the "issues".
There is currently a single-owner, all records and well-maintained C55 that has my eye for a good price. I may have to give the E55 another shot though. Even my wife said the C was too small. It reminded her of my old '04 Saab 9-3! Ill keep you posted!
'91 E34 M5
Dinan 3.6 Stroker, Tune, Exhaust, Sways