Unless I'm mis-informed, most of the weatherstripping is made by Precision, so shop where you like to. (my information came from multiple web postings and the local GMC dealership. Parts guy told me to shop around, I could probably as quick or quicker than he could. For the same box.)
The complete kit does not contain the on-door strip. LMC does sell it separate (maybe, catalog says 79-81?) I did the weatherstrip abt 5 yrs ago on the '73. My door strips were in decent shape, so I re-glued them on.
LMC- page 15 (bottom diagram, #5) part #,38-6948 (LH) 38-6949 (RH)
Just happen to have the catalog in hand.
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'86 C-30 dually, 454/tbh400
'73 K-20 350/350/205 (sold
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I'm kinda like duct tape- no real purpose, but handy to have around.