The 1947 - Present Chevrolet & GMC Truck Message Board Network - How to convert your early cab to accept modern brake master cylinder

I took some pictures today as I worked on my truck. It's too hot to work now, so I figured i would do a little tech piece for anyone who has an early cab and wants modern brakes.

My cab is a 62 model. It's the one that takes the dual master cylinder and clutch cylinder combo. I am running a turbo 350 trans now, so I have no need for the clutch part of the deal.

Problem is, the early cabs use a funny diagonal bolt pattern and later model master cylinders use a horizontal bolt pattern.

First, this is the beginning before teardown...
http://i276.photobucket.com/albums/k...63chevy118.jpg

Once the old dual master cylinder combo is removed, you are left with this. None of the holes are conducive to modern units...
http://i276.photobucket.com/albums/k...63chevy129.jpg

This is a later cab (a 63). Notice that along with the funny diagonal hole pattern, there is the horizontal pattern we want...
http://i276.photobucket.com/albums/k...63chevy130.jpg

First, we need to weld up all of the unnecessary holes. Just leave the 4 pictured here. Notice I painted the firewall between pictures, but it's the same early cab as the first picture...
http://i276.photobucket.com/albums/k...63chevy157.jpg

So, I removed the brake pedal box from a later model cab, cleaned it up, and fit it to my early cab. The later pedal box is a straight bolt in other than a tiny bit of grinding needed around the old clutch hole. You can see in this inside shot where I had welded a round patch into the old clutch hole. You will need to grind a bit on the little lip around the old hole...
http://i276.photobucket.com/albums/k...63chevy167.jpg

Outside pic, note the newer box bolts into the same 4 holes we left...
http://i276.photobucket.com/albums/k...63chevy165.jpg

Go back inside and backdrill the two horizontal master cylinder holes, through the bracket and through the firewall. Here is a punch in one of the spots...
http://i276.photobucket.com/albums/k...63chevy168.jpg

The other hole that needs backdrilled...
http://i276.photobucket.com/albums/k...63chevy169.jpg

Now, all you have to do is bolt the later model master cylinder into place and you're ready for disc brakes..
http://i276.photobucket.com/albums/k...63chevy171.jpg

No real money spent on this deal. In my eyes, this is much better than ordering a kit from some place.