I always try to figure out how to accomplish something without help. I have not done a sunvisor, but you may need to fabricate a holding fixture of sorts, maybe using 2x4's and some clamps and nice padding. As far as centered etc. Use masking tape to mark on and measure from some reference point that exists on both sides of the cab. And again may have to be a straight edge held with a 2x4 frame support of sorts. The engineering is part of the fun. Also for horizontal a level could be used, the truck will of course need to be level to do that. If its a curved surface you may need shims the same size and located the same distance from center etc. Also refference measurments down to the hood or cowling. Take it slow and easy. Triple check.
