[Rachelsdad]

Better late than never...

So, if we consider:

1. The Star Chief is a model 26 and Bonneville is 28
2. There are Star Chief 4-door vistas and 4-door dedans
3. There are Bonneville convertibles, coupes, vistas, sedans, and wagons

then the frames are only slightly different in dimension at the very front of the chassis, as stated in the first picture. I don't think that .015" difference would really mean a lot in the real world. We know that the front end sheet metal is the same, and this is the reason we have shims for body panels.

I've included a couple other pics stolen...er...borrowed from the shop manual, as well. The bolts all go through the same places for sedans. Convertibles are different by necessity, of course, as they lack upper rigidity by comparison.

HTH