How rare is a 68 c10 w/396/TH400?

[SB_in_SC]

The unit I am speaking of is the dealer add-on type. The under-dash unit, which I believe had 2 registers. (I stated "factory A/C, but I meant "dealer add-on") I would not consider changing the dash, even though it would be hidden as dtlilly said. Its just that the unit is FREE and would be just as you could have ordered it from the dealer. Just wondered if y'all thought it would be wrong or might detract from the original resto value of the truck by adding the "dealer add-on" unit. I would love to have A/C, but not at the risk of detracting from the value or "spirit" of the original truck.

Thanks to dtlilly and sixty8c10 for the response!