Beware of Boat Anchor Companies masquerading as ASME certified boiler manufacturing shops. I personally know of 3 locomotive boilers permanently sitting next to the intended frames for which they cannot be physically married.
Investigation into one ASME certified boiler manufacturer specializing in locomotive and traction engines has led to the DECERTIFICATION for non-Code compliance of at least 7 completed and Code Stamped boilers.
Many shops have the capability to build locomotive boilers, but not the engineering expertise to properly design a boiler in full compliance with all the intricacies of the ASME Code and know the critical dimensions which must be maintained for proper fit into the frame.
Serious background check with previous customers is a MUST in deciding on a locomotive boiler manufacturer.