Since you're not opposed to jap swaps how about a Toyota 22r or Nissan 2.4 ? Both came in trucks w/ 5 speeds. Cheap & easy. Not sure how fast you could make them, but should be fun to drive. Or maybe a 3.0 SHO Taurus v6. Not so cheap & easy but a high winding engine you can hook to a Ranger 5 speed.
A small V6 like the one used in Rangers and Explorers, same one used in Mustang II's and Pinto's should fit. They are short and narrow, and came in sizes from the 2.8 to the 4.0. A 4.0 with 5 speed in a Ranger is a torque monster, lots of fun. The early ones had a 2 bbl, later ones are FI.