Super nice 66 Valiant for sale....

So, what if the brakes were off a 70-72 ?
Then yes, it would definitely be the wrong mc.
Lot of variables we don't know.

Anyways, the more I look at it, the more I like it.

I wonder what that radiator is out of ?

It wouldn’t matter if the brakes were from a 70-72 as long as they were K-H. The 4 piston setup doesn’t need near the reservoir space like the single piston design.