Heat Shield holes in 4x4 cab???

[DANTIP]

Shown below is a stripped cab from a frame-up restoration of a '72 4x4. The SPID didn't have A/C listed and I was questioning the originality of the cab. The owner sent me a few pictures and it certainly looks like an original A/C cab. Upon closer inspection, I noticed holes in the cab floor on the passenger side that would have been used for a heat shield on a Big Block truck. The VIN tag is riveted to the cab with the rosette rivets and looks "original".

Assumptions:
1) The heat shield was a big-block only item.
2) High-hump trucks without the heat shield did not have the holes in the floor for the heat shield.
3) There is no other reasonable explanation for the heat shield holes other than the cab was originally on a Big Block 2WD truck.

This may not be important to too many people, but this is an expensive truck and I am willing to pay more for an original truck than one that has been put together from multiple donors.

Lastly, is there any other differences I can look for in these photos?

Thanks for your feedback!!