rear end/brake swap

[Kent]

I've installed a disc brake limited slip rear end from a 1983 into my 1979. The brake balance is now off.
I'm looking at the manifold from which the brake lines exit and which is attached to the passenger side of the master brake cylinder and wonder if that manifold is a proportioning valve. If so, I'd think that it needs to be changed to one from an '83.
Any advice to get the front and rear brakes balanced would be most appreciated. Thanks

[black rocket]

Yes, the unit is the proportioning valve.