It seems to be a bit of an urban myth that BLW built the K-37 chassis. I've seen coorespondence from Burnham relating to machining frames and etc. for "converting 1000's into narrow gauge engines" in the late 1920's. 497's cylinder block has a manufacturing company's name cast into it. It was a well known foundry in the Denver area. Perhaps BLW furnished rough cast frame members, but the rest of it appears to be Burnham's handiwork.
IIRC American Steel Casting was BLW's foundry subsidiary.