5.3 In 1948 Chev Pickup

I am installing a 2007 truck 5.3 into my 1948 Chevy pickup. The original 5.3 cast iron exhaust manifolds did not work out, dumped on top of frame rails.....So I got a pair of center dump cast iron exhaust manifolds from a Camaro. These Camaro cast iron exhaust manifolds has the oxygen sensor located on the top side of the manifolds just over where the exhaust dumps into the tail pipe. Is this location for the oxygen sensors okay for the 5.3 or should I place the oxygen sensonrs in the exhaust pipes aboud 18 inches from where it bolts to the exhaust manifold?

Larry