curioustom

Hello! New to forum but have visited often. Longtime Mack fan with some basic questions. What do the model names mean? For example B61, B81SX etc... I am very partial to Superliners and LTLs. Have seen numerous pictures of B81 SXs, or anything with the flat "gravel pit" fenders. Any info will be absorbed like a sponge, you guys have so much knowlege! Are there any publications availabe with this sort of info? what model is this in the attachment? (if I did it right) Thanks in advance!