Looking for an Intake Manifold

I need to find an intake manifold (part #ECT 9425 C) believed to be off of a ford truck. I am rebuilding a 53 lincoln for the panamerican race and have hit a wall. Also, if I could just find out what motor this manifold came on, that would be a help too.

I've seen just such a manifold on eBay two weeks ago...it was heavy and shipping was outrageous!! Just keep watching ebay for a while...one will appear.

do the rules limit you to a stock-type cast iron manifold?