Another JR: Sounds like you have the same truck I'm looking at except I need a regular cab, long bed. The spec on the GMC website is 80.67" for your truck. So you think the height spec includes the sharkfin? The reg cab, 8'bed, cab height is 80.94".
If that includes the sharkfin, I'd have a whole 3/4" clearance! Lordy! I guess one could order a truck without the satellite antenna to get a bit more clearance. Sure would miss the Sirrius. Also thinking I might pick up a bit of clearance with the driveway apron matching up to the garage floor at a slight angle, but can't tell without a test fit.
Thanks for the reply.