I have never seen a shroud for a 6 cyl or even seen brackets to put one on even working in a wrecking yard 20 years ago when they were still all over the place, I'd like to see a picture of one if any one has one or knows where to go.
I have a couple six cylinder fan shroud extensions, that the original fan shroud attached to. I don't have a photo on my computer, but I will take a few and post them. I have seen them loose, as well as, installed in factory-equipped six cylinder trucks...and I never worked in a salvage yard, but I have owned, collected and restored '60-'66 Chevy trucks since 1981.