NCbob, I just suffered through the same experience with my 1984 9. Here is what I did. I was able to secure 4 inch and 7 inch LEDs 24 volt from: http://www.etruckpart.com/index.htm
When ordering see if you can get the slimmer version of the 7 inch light. Each 7 inch light was $44.00 The red and amber 4 inch lights were 24+ per. The pigtail connections were important to me as they are water tight, yet replaceable. In addition, these lights come with a lifetime warranty! They are rated specifically for 24 volt systems so I maintain my warranty. The wiring followed my schematic and I was able to make several grounds into one common ground connection. Made it look better and professional. I also wanted to make sure I could keep the original housing and not have to make modifications the original look of the bus.
Each light works awesome and look fantastic, particularly at night. I went with the lights with the most LED per lamp as I wanted brightness and visibility.
I have only run into a bit of a problem with the front turn signal lamps. The original housing unit and light assembly are not standard sizes. I have found a standard LED lamp and will modify a 5 inch stainless steel washer to act as a retainer for the lamp. They too look awesome at night and are 24 volts.
I can send you pictures if desired.