Whoo... the mind reels at the thought of
a.) Calling you boss to tell him you are trashing three years of work, tomorrow
b.) Likewise claiming that you will have all that redone in 90 days and still make the drop dead tool release schedule
c.) Your team will be knocking out brand re-defining work on practically every model
The '59 re-rack was the function end of Earl's reign in Detroit, a soft putsch by Mitchell and his studio heads to assert a more modern look to GM products.
Yes, Buick was across the line first with their clay, although, cynically, I'd wonder if there were not sketches in top drawers of the key designers that were initially rejected in favor of the vulgar and bulbous '58s that got refreshed and re-presented as 1959 product. Would not be the first time in Detroit that an idea found its time in crisis.
The cowl and windshield are very expensive, deep draw parts that require expensive tools and transfer lines.. They also locate steering columns, HVAC, braking, electrical, etc so it is logical that GM was cutting out a lot of the duplication that made earlier models unique to each division, a lesson they would learn that would reap tremendous profit.
From a manufacturing perspective, it made Fisher's job much easier to start building guages and jigs, which would be needed, oh, yesterday. Thus, there is precedent for doing a lot of swapping.
For a 'pickup' Pontiac, however, did not have a two-door panel delivery or stawag to do the conversion. IIRC, they used the long, sweeping Converitble 1/4s with the stawag rear section / tailgate area, which would require quite a bit of fabrication work. But Detroit was soaking in that capabliity at the time, so that job would be fairly straightforward to prototype fabricators.
Ultimately, the question would become, what other Pontiacs would be taken OUT of schedule to make a fairly low running pickup version? Once every dealer orders one as a parts chaser... then what? I'm not dissing on the product, in fact, it pays off the double fin rocketship look nearly as well as the bubbletop coupe, and looks less bizzare than the Elco ("Mommy, something is eating my bicycle!!!)
In kit form - you would need to hope the transitive property was doing its thing and designers were on point in their measurements. Not that you couldn't Elco a cast off Bonneville convertible (hmmmmm, Bob said,) but the difference between annual kits that were box-scaled in some cases, and the "Trophy" kit Elco that came later may be just enough to confound the project.
Stikk, SOMEONE did it, and there's no reason that there would not be an opportunity for the courageous to take a swing at the idea with the saw, CA and filler. Personally, someone with Geary-level 3D chops would probably be able to knock the subject out and do quite well with it commercially.