Ok, this is interesting. There were at least two brackets through the production run of LV’s. My 1964 frame does not have the three holes needed to mount one of the later brackets like yours. (I still want a set, though). The first four pics are from the 1963 45V parts manual. Unfortunately, this 1963 manual uses the old part numbering system and I don’t have a cross to the later system for this part. As you’ll see, there was an early style with long brackets that dates back to the FJ35LV and an optional setup with a bracket that seems to mount straight off the back of the crossmember, but we know it can’t work quite like that. I’m wondering if the early frames have an additional welded or riveted bracket that drops down from each end of the crossmember for the brackets to bolt to. My 1964 frame shows slight remnants of some booger welded brackets that were probably welded on later by a PO.