'29 pickup cab mounting blocks.
 

I bought a set of mounting blocks for my '29 open cab pickup. The rear mounting blocks -- the ones that go under the cross subrail at the back of the seat riser --don't seem correct. Each end of the cross subrail has one hole on center, but the blocks have a pair of holes, and they're not in the center of the block (closer to one edge). No matter which way I turn them the holes don't line up. The vendors catalog didn't differentiate between the blocks for open and closed cabs, so I'm assuming they're the same, or not? Anybody got an idea what's going on here?

Bob