Here is what you want Dave. Peterson LS7 breather 08-0400-ATS. The large fitting goes to the top of the oil tank. The two smaller fittings connect your two valve cover fittings to the air intake tube (between the maf and throttle body).
I have a sneaking suspicion that the two sided mounted fittings are just connected in a loop internally in that Peterson breather can for convenience. If so......there are much cheaper ways of accomplishing the same type of hook up.
If the above scenario is true then just purchase a simple breather can like Grant shows. Then tee your two valve cover breather connections to the air intake tube (between the maf and t body).