Need help with rear disc swap

[VictoriaHardware]

This site has a ton of excellent info- http://www.pirate4x4.com/tech/billavista/Brakes/

About 3/4 of the way down the page is a downloadable spreadsheet. You can put all of your variables in and get a good idea how your truck's brake system will work before you ever buy the first part.

I followed it and recently completed a 4 wheel disc conversion on my '66 C10. I too used stock GM truck front calipers, Corvette 1.125" bore master, and Eldo rear calipers. I too had an awful time with the rears but finally got it. Now the whole system works very well. Put in your info and the spreadsheet will convince you the front caliper and master you have are correctly sized. It will also convince you the Astro rear calipers are too big diameter-wise.