Unless you're using a GPS for your speedo you shouldn't see any variation between speed and rpm with different sized tires. You will be going faster with the taller tires though.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k