I have posted the following information some time ago on this forum, relative to the X Frames , 58 -64 chevrolets . In view of the fact that some of our members missed this information, I will post it again, as the question about the X frames continues to come up: In 2010, I spoke with Vern FRANTZ about this subject and here was his answer::: "The rumor about the boxed frames being Canadian , has been around too long ! There were three suppliers of frames for our Chevys: A.O. SMITH-They made the open channel frame for CONVERTIBLES. BUDD COMPANY- They made an open channel frame for all other models: CHEVROLET (or Detroit)- They made the boxed frame for all models EXCEPT convertibles.
NO frames were made in Canada. But since Detroit is so close to Canada, it's possible those were the only frames shipped to the Canadian assembly plant, thus, they became "Canadian" frames" End quote. Hope this is helpful . Mike