GM-GMC: brake system of 79 gmc k1500, vin number, information kits

Question
I have a GMC K1500 1/2 ton 4x4 5.7L 350. I would like to know how to find out what type of braking sytem it has in order to find the correct master cylinder, or if you know it that would be great. The choices for the braking system are JB-3,JB-5 or JD-3, JD-5. The vin number is TKL149F722738, also the truck is a trailering special with the 2.75 in. rear drum breaks if that is any help.

Answer
if i still worked for the historical department of gm i could find this...

here is a site that might help you
http://www.gmheritagecenter.com/gm-heritage-archive/vehicle-information-kits.htm

if nothing else call gmc and tell them you need to find info on a old vehicle and they should be able to send the request to the history department and get an answer.

im sorry i couldnt be more help
good luck