Hello people. I have a 91 Ranger that was originally my dad's. It has a 3.0 V6 that is shot, and the tranny has seen better days. I have an 04 Freestar with a 4.2 at my disposal. I know I will have to get another tranny for it, but how difficult would it be to swap the engines?

 

Welcome to the forum

Problem with most engine swaps in our 1983-2011 Rangers is WIDTH
They have a narrow engine bay

Ranger V6 engines were all 60deg Vs, so narrower
The widest engine used was the 4.0l SOHC at 19" wide

Ford 302(5.0l) OHV was 90deg V but doesn't have over head cams(OHC) so was 19" wide, so fit in Rangers

The 4.2l is 25" wide with OHC, I believe, you should check/measure that, since you have one
Which means you would have to remove heater/blow box in engine bay, so no AC, and also move the steering shaft over a bit, to get the 2.5" on each side, would also be tight to get exhaust manifolds on
Stuff a larger engine into a tight engine bay is one thing..................servicing it also has to be has to be considered

And you do need the 4.2l computer and wiring of course, also the transmission, M5OD-R2 manual trans from a 1997-2003 4.2L F-150 will work