Hey thanks Bob. That certainly looks very very similar to the tank we have. It looks like the tank strap recesses are angled, where is ours are pretty much squared across, but that really would be a problem. I can't remember on a 55-57 which side the tank inlet is on, however if worse comes to worse that could be changed also. The gas inlet on the 49 is on the left (drivers side).
Thanks for the input, possibly one of the reproduction companys could give me some measurements on 55-57 tanks.
Appreciate the help.