Here's a couple of things for you to check:
1. Headliner. Factory installed headliner will have a chrome painted plastic trim piece around it. If it's missing, you should still have slotted holes in your inner cab roof skin that the headliner trim clips inserted into. If the trim is there, check to see if slotted holes are under it. These holes will be neat and uniform and elongated if pre-drilled at factory. It is possible that someone went to the trouble to drill holes after the fact but they won't be perfectly uniform (unless the PO was really anal about his install). If you don't have these holes, your cab was not a Cheyenne cab. CD's could not be ordered with a headliner as it was a Cheyenne/Cheyenne Super only item.
2. Cheyennes and super's came with carpeting. CD's would have color-keyed rubber mat. The lone exception is the Highlander equipped CD. This had black carpeting included as part of Highlander package.
Another clue is you say no lower trim. Cheyennes and supers had upper and lower trim as part of the package.
Another possibility is that your truck is simply a highly optioned Custom model. Your sticker has a # next to the SE which usually indicates a special order, i.e. the buyer ticked off the options he/she wanted and the factory built it that way.
As for the paint, here's a theory based on the possibility I pointed out above:
There were 2 two-tone options. One had white top and white on sides between upper AND lower trim. The other option was similar, except white top with white below LOWER trim. Either option requires lower trim to mask the paint lines. It is possible the purchaser ticked the 2 tone box but was never instructed that the lower trim option had to be ticked as well. It went to the factory as 2 tone and got into whatever computer system spit out the rpo stickers. However, at the time paint was to be applied, somone noticed the lack of trim and "deleted" the 2 tone as a factory line decision even though the sticker still listed it.
Another tell-tale 2 tone clue is a chrome trim band behind cab. This was added again to mask the paint lines. If your cab had 2 tone it would have the trim or at the very least it would have the pins welded to cab to hold trim clips.
Anyway, iteresting truck. Any way to get a clearer pic of the glove box sticker?
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Currently on or near the homestead:
67 Chevy SWB 2WD stepside 350/3 on tree (Pat's)
67 GMC SWB 2WD Fleet 402/auto (Brian's under construction)
67 Chevy 3/4 ton 2WD 402/auto (Business Hauler)
67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC)
68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC)
70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC)
71 Chevy SWB stepside (Crushed by tree - parts donor)
72 Chevy 3/4 ton 4WD (Parts donor)
72 Chevy 3/4 ton 4WD Suburban (Parts Donor)
72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC)
81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler)
82 Camaro Z/28 355/Super T-10 (Pat's toy)
93 Caprice 9C1 (Brian's Cop Car)
02 Toyota Camry (Reliable but a souless steel and plastic hulk)
2011 2SS RS Camaro M6 Factory Hurst Shifter
Maybe I need to sell some of this crap
Yet another Bozo with a sawz-all