There were three distinct versions of the passenger car/commercial vehicle front cross member. The first two were without stamped-in depressions for the third and common version of the front motor mount insulator and are usually referred to as the 'flat' front cross members. The difference between the first two was in the number of holes for the motor mount insulators, The first had two small holes placed diagonally on each side to bolt in the first version of the motor mount insulators. The next version had both the small diagonally-placed holes plus a large hole centered between the small holes. That cross member could accommodate both the first, second, and third version of the motor mount insulator. In the case of the third and most common insulator there use necessitated the use of a large separate cup washer which was utilized briefly before the stamped-in depressions were added to the cross member. (The same cup washers were used again on the '35 and up front cross member.)
The big truck cross member could be mistaken for the passenger car/commercial vehicle cross member at first glance. On closer inspection, it is not surprisingly of heavier gauge steel and it differs in where it is riveted to the side rails and in the spacing of those rivets. While I have not seen three different versions of it, it would seem reasonable that the same three variations of it existed as with the passenger car/commercial chassis cross member given that there were no unique BB motor mount insulators. Understandably, the big truck and passenger car/commercial vehicle front cross members are not interchangeable.
