36-6019 master cylinder kit

[wgiles]

I'm rebuilding the master cylinder on my 36-6019 Cadillac 4 door sedan and the kit installed looks identical to the Raybestos MK-3 kit. 
http://www.jcwhitney.com/p2022732/sku-667437.jcwx?TID=gglpla&gclid=CIydxqu8pc0CFQctaQodaccF-Q

I also have a Raybestos 197 kit.
http://www.jcwhitney.com/p2022732/sku-667388.jcwx?TID=gglpla&gclid=CJr87oq8pc0CFQcMaQodN80Cig

The only difference is that the MK-3 kit includes a check valve and rubber washer and the MK-197 does not.  I've had problems with the breaking since I've owned the car and I'm wondering if the wrong kit has been installed.  Does anyone have any experience with this problem or know which is the correct kit?

[TJ Hopland]

Were they doing the same but different thing back then like they did later with the Bendix vs. Moraine?  I have run into that before where there are just little differences and the wrong kit really messes things up.  Omitting the check valve in one version seems odd but I really don't know much about that era.   Was it maybe some sort of field update?  One kit fits the original version and the other an update?

[wgiles]

I don't think there were two different versions to the design.  I suspect that maybe the previous owner installed an incorrect kit, which included the check valve.  My problem is that I don't know what the check valve is for.  The original design is what I'm looking for.  The question is whether the original design called for a check valve or not?  The service manual shows the internals but does not identify a check valve.  That's what makes me suspect that it is not called for.  See attached pdf.

[wbdeford]

Careful buying modern brake kits for old systems.  I bought a Napa one for my '58 that supposedly works for Delco Moraine, but wasn't even close.