I sold a open plane aluminum SBC intake that had been bead blasted to 'newness" and was even Zyglo'ed for cracks, I couldn't give it away.
I finally had a guy pick it up for $50. Look around you will find similar deals for used AL intakes.
This fits into the "redesigning the wheel" category and although you have the time and inclination is not worth the hassle and medicore performance gains you will see with a fabbed intake manifold. Lots of testing went into the design of an intake manifold and you don't have resources to duplicate the effort.