A raw as cast adapter could make your fit up a little easier when fitting 4/71 GM supercharger to 142 supercharger flange intake manifold. You are buying an unmachined casting
This adapter was designed to mount a GM 4/71 supercharger back to Weiand 142 style manifolds, the centre discharge hole is tappered to fit both superchargers. It has also been used with the centre machined out and tig welded to other manifolds and used as a spacer to increase the height of the plenum on a 4/71.
4/71 opening 97 wide 170 long
142 opening 65mm wide 254mm long
You are buying the adapter only, it does not include gaskets or studs