What is this canopy called? Is it a factory option?

[Dooley]

What Keith said.

GM and or the dealers over the years have offered incentives for buying pickups when sales were slow. Many times it's buy a truck, get a free bedliner. When I bought my new 1988 V30 they were offering a bed cap or a bedliner with the new platform of GM light duty trucks. My dealer had a recent square body trade with a nice cap and he offered it to me for my truck since they didn't have those available. I was happy with my freebie.