Welcome to MFK!!!
I take it you mean a SAL (Lepidosiren paradoxa). SALs are the best candidates for a community tank, as far as LFs go. But, with any predator mixing, there's always a risk. If a LF ever decides to sample a tankmate, the chances of survival are very slim.
BTW, I hope you realize a 55 isn't going to last long for these fish. BGKs usually top out at a foot in aquaria but, can reach 19". SALs are tank busters reaching the 4ft mark.