thoughts on the edelbrock sp2p manifold

No really, how are you going to put 2 carbs one 1 intake? There used to be multiple 2V intakes in the 50's but the WCFB and 4160 Holley made those pretty much pointless.

If you insist on this, use whatever manifold is cheapest. It won't be your stumbling block to performance or economy. 2x2bbl will not run OK, it will be a headache.