Transmission swap NV4500 into 1982 W250

Looking for anyone who has made this swap or similar swap in older Dodge pickups. Right now we're running 360 CID V8 built for torque with an old granny 4
speed. Do you have to have an adapter to put Dodge model NV 4500? Axles are Dana 60 Front and Rear with 4.10 gear ratio. Truck is turning around 2400 RPM's @ 45 MPH. Tires are 33"X 10.5", will be switching to 37"x12.5". Can someone tell me what the difference would be on speedometer and approximate RPM's with 2" tire circumference @ 45 MPH. Any help would be appreciated. Rick
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