Usually people want to go the other way, to a lower profile tire...your question is unique in that respect. Your speedometer will read slow. The -75 is the aspect ratio of the tire dimension...read as the percentage of the tread width (the 265 part of the size...in millimeters). A higher aspect ratio means a taller tire from the larger diameter, meaning a bigger circumference. Thus the tire doesn't have to rotate as much to travel the same distance. At that aspect ratio and the amount of the change, change in ride quality would be minimal...mostly softer and probably more wallowy (is that a real word?) since you have more sidewall to flex as you take bumps and curves.
If you wish to keep your speedo within calibration and stilll wanted to go to a taller tire, you would need to find a 245-75R16...slightly narrower. The narrower tread would lend to its own handling issues and possibly towing limits.
IMO, I'd reconsider the size change, but a little more info on why might make the justification. In any case, I hope this helps!