[Christ]

If you want to change rear gears, and you have an 8.8, get your new gearset from an Explorer. They've all got Limited Slip Diff's in them.

The 300 has enough torque to keep the truck going 60MPH with way less RPM than the OEM gears allow for. The OEM gears, I think, assume that you're not going to be doing too much driving on the highway with your new truck that was designed to WORK, not DRIVE. The F-series pickups of the days of yore were always workers.

You can swap in any 3.8 V6, 300 I6, 240 I6, 302 V8, 351 V8 transmission you find, as long as you can make the trans x-member fit between the frame rails, and you have the correct clutch disk for the trans.

One of the nice things about the 4.9 I6 is that they're all cast iron, pushrod, inline engines. They can idle really low, have torque just off idle, and if you put one of those trucks in low-lock, you can move the earth, just about. With the engine at 5500 RPM, my father can walk faster than our Ford in 1st gear LowLock. You can heat them up fairly high, and they'll take the heat like a champ, and keep on running.

It's gotten so bad in our Ford that the plastic vacuum lines on the I6 started melting and warping... and it still was running fine.