78 3/4 ton Master Cylinder and Proportioning valve question

[Yukon Jack]

I have removed a manual brake master from my 1970 K5 and have installed a master cylinder, booster and proportioning valve from a 1978 3/4 ton.

I removed the donor parts quite some time ago and I don't recall which reservior is supposed to feed the front as opposed to the rear.

I currently have it hooked up with the front reservoir going to the proportioning valve to feed the front brake lines.

Can someone with a 78'ish 3/4 ton take a look and see which reservoir feeds your front brakes? I believe your proportioning valve should be on a crossmember about below the engine fan.

Here is how mine is presently ran



Thanks