X...Dual quads definately draw attention. I recently installed a 2X4 setup on my crate 460. I used a Blue Thunder manifold and two 600 Holleys with 427 linkage I purchased from carlsfordparts.com. Although you have more cubes the parts are still the same. I also gained another inch of clearence to the hood scoop with the slightly lower BT manifold. The Blue Thunder is cast with 429 size ports so to correctly fit to your 514 with im asuming you have the Aluminum Cobra Jet heads they should be opened up to port match the cylinder head. I learned this info before I took on this project from SFfiredog...thanks Mike
Tony