E-brake different from a 78 to a 80? .also proportioning valve question

[sircrunch]

I'm swapping the frame on a 1978 v8 big 10 shortbed. The donor frame is from a 1980 6 cyl shortbed.

So I'm finishing up and I noticed something strange when trying to put the e-brake cable back together. The ebrake cable part that hangs out of the firewall looks like it mounts to the chassis in a different location on this frame. You can see where the 80 model mounted, but the cable that comes out of the firewall on my 78 cab does not reach this bracket. Any advice?
Also, I'm keeping my Big 10 style brakes front and rear (heavier duty). I'd like to use the same brake lines including proportioning valve and everything from the 6 cyl regular duty brakes. Are they the same?