I just purchased a 1997 Ford F150 4x4 and want to get rid of the mudders that are on it (boy do they sound and drive bad) because I mainly drive On-Road except for when I go hunting and fishing. I am looking at the BFG T/A KO's size LT265/75R16/D to put on the stock 16x17 rims.

Is there anything I need to do because the truck originally came with P235/70R16SL tires? Can I adjust my speedometer? Will this effect my engine performance?

Thanks