I may be wrong, but I think you can delete it without any ill effects. Failing that, I would imagine that any proportioning valve can be used since brake lines are pretty much a universal size. Only thing would be a possible difference in brake pipe nuts/flare.
1966 109 5 door wagon 300Tdi "spermaceti fueled"
1994 RRC LeWiB "ruining the air behind me"
1968 2A 88
All my troubles are Rover