1977 K10 LB stepside Did they build any?

[3x2GTO]

I'm looking at buying a 1977 K10 short bed stepside from an estate, it looks to be original, except it now has a fleetside bed on it. I checked the decal on the glove box and it came equipped as a Scottsdale, stepside, 350 4bbl, 4 speed, K10 with AC, all of that is still present. The problem is, I forgot to check the wheel base info on the decal, to verify that it's a factory short bed and not a cut down. The estate is also selling a nicely done, home made trailer, built from a square body, long bed stepside pickup frame & bed. After I got home, I got to wondering if the bed on the trailer, originally came from the K10 pickup I'm looking at? I looked at the K10's frame fairly well, and I didn't see any signs of it being shortened, but I really need to go back and recheck it. The truck isn't close to me, otherwise I'd drive over again and check it out more thoroughly, before getting the $$$ and trailer together. So, my question is, did GM ever build a 1977 K10 long bed, stepside pickup? Also, the stepside bed on the trailer looks to be an 8 ft, or maybe 9ft with a wooden floor.