What model year trucks are you talking about?
If its first generation Tacomas and below the SR5 package was an option package that was normally loaded with power windows, power lock, cruise, tilt, cloth or sometimes leather seats, carpeted floor mats, some vehicles got accent stripes, and sometimes the package included an automatic transmission.
SR5 was availabe on certain car models too.
The later model SR5 packages are more dress up since almost every vehicle manufactured has those conveniences standard.
Pre Runner trucks were first manufactured during the first gen Tacomas.
Pre Runners were built with the suspension of a fourwheel drive minus the transfer case, front d/s, front differential, and front half shafts. The front spindles were specific to Pre Runner trucks also.
A Pre Runner truck can be coverted in a long weekend by adding the afor mentioned items, their all bolt on.