Try checking on
http://car-part.com/ and remember you can use the distributor from any Isuzu with a 1.8 or a 1.9 engine which includes the Imark, Pup, Trooper, Luv, Impulse, some early S10's, Trooper, etc. I originally used an early style one from an Imark (the one with the ignition module externally mounted on the coil), but later switched to a newer one from a Pup ( which has the ignition module mounted inside the distributor cap) - but either one will work.
Also...don't forget that when you find a 5 speed it has to be from a RWD 2WD vehicle and you will need the driveline yoke that comes out of the rear of the tranny to connect it to your driveline. The stock 4 speed and the 5 speed's yokes have a different spline count. The drivelines are the same and the u-joints are the same too, but the newer driveline's rear yoke won't bolt to the stock Luv's rear pinion yoke either because the bolt pattern is spaced differently. The 5 speed came in some early S10's, RWD Imarks, Pups, and Impulses.
These will help you to sort it all out:
http://www.luvtruck.com/pdf/CHEVY_LUV_7 ... CHANGE.exehttp://www.luvtruck.com/pdf/Chevy_1972- ... _parts.exeJust right-click on them, download them to where ever you want, and double-click on them and they will unzip themselves so you can take a look at them.
Here's the how-to article on making the distributor swap:
http://www.luvtruck.com/pdf/LUVignitswap.pdfJust right click on it and download it. These three files are all Adobe Reader .pdf files. You can download that for free if you don't already have it, or download Foxit Reader:
http://www.filehippo.com/download_foxit/(It's a lot smaller, loads WAY faster, and IMHO reads .pdf files much better.)
I got real lucky when I found my running gear for my '78 Luv shortbed stepside out of a '87 Pup and I got the whole tranny, rearend, driveline, etc. real cheap, so I swapped everything out at the same time.
Good luck and happy hunting!