[Gunner]

Only other thing you can do if the ravs worth it is drop the tank out, drain and wash it out for safetys sake. Then cut or drill the bolts if the heads are rusted away and try to extract the stubs with a pair of vice grips if enough left to grip or if not stud extractors. The studs themselves should not be seized in the tank just always seem to be the heads rusted away on the bolts as I found mine were similar but I was lucky enough to get them out.