I can add a few bits of info, from times I've talked to Cecil about the cars - I've known him over 30 years and have done a little work on his re-creation of Missile VII (the original tub was used up & scrapped, but he kept the usable parts)...
The 1st 6-8 '64 "2%" cars were handbuilt, and the math actually worked out to 6% - the 2% was an NHRA rule, which some of the Fords also exceeded. Lightweight "glass" & no vent windows are indicators, as FMJ says. 12 Magnesium K-frames were sent to the contract racers, and at one point stainless Ks were also sent. For a time the ft spindles were 4" taller, Valiant brakes were used (!) and it took 3/4" of toe-in to kind-of-work. Most of those parts were demanded back by Chrysler due to problems and/or development of newer pieces. Typically, Monday morning phone calls reporting results would also initiate shipments of new stuff.
When Missile VII was converted from "2%" to the 10"/15" configuration - which was done in NorCal - Chrysler sent them an RO car to cannibalize for parts. It had a fairly plain fiberglass dash, but Cecil said he never got a "bubble" windshield and doesn't really recall them; that may have been a limited experiment, as a photo of at least one exists. The contract racers running the cars were constantly tweaking & lightening them, so some details depend on the specific car and the week. Also, parts were sometimes handed down from one racer to another, so a hybrid or two existed. One oddity is the different side profile of the RO/WO Hemi scoop and the one most of the 10/15 cars wore.
There's a video clip I've seen of Cecil in Missile VI @ Famoso, which was a '64 "2%" car - the thing goes hard right almost immediately, into the push-start road on the right. He said Chrysler blamed it on the front-end setup & demanded those parts back, but the real cause was the 8.75 bending.
FWIW -here's VII as it currently sits at Cecil's shop.
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