Will a 302 Ford engine fit in an older model Ford Ranger?

With significant modification, it is possible. However, it requires a good bit of work like squeezing it between the fenderwells, modifying the motor mounts, upgrading the transmission to handle the HP and torque, moving the crossmember for the tranny, and setting up the right driveshaft. In addition, you may want to upgrade to Dana rear ends in the front and back so you don't send the ring and pinion clean through the rear end cover.

But yeah, it's possible...

Http://www.therangerstation.com/tech_library/index.php
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This site has loads of info about Ford Rangers. It will probobly give specific answers to what modifications are neccesary for your 302 swap.
I remember reading that the 302 is about as big as you would want/need to place in one. Is the Ranger 4x4 or 2x? Dirt? Street? Everyday driver? Track? Show?
-With this much motor, you may wish to do something with the gearing