How rare is the GMC Sierra Grande?

[Longhorn Man]

You'll never know how many grande trucks were made, the documents were lost. That IS a rare find however. GMC trucks were more likely to be middle of the road as far as options... they were built more for work than play.
You say your truck is unrestored... there's a few items that are not original, and make me think some one has done a restore... or a lot of repair/parts swapping on it.
That tail gate is a recent aftermarket piece, the side trim should have wood grain... not a bright finish like it does, and that speed warning wasn't avalible after 69. The mirrors and wheels were also added later too.
Please don't get me wrong...that is a super sweet truck, and I can only hope that mine will be that nice one day... but there's a good chance that many of those were added. Is the option list still in the glove box by chance?
The wood grain you mentioned is correct for the Grande, as is the upper and lower (with woodgrain) moldings, the 2 tone and guages...all part of the package. The A/C, buckets W/console, shoulder belts...all added options on top of the package.