If you can find it, Sunset Mustang's "Ford High Performance Parts Identifier" booklet is great. Author is Robert M. Winkelman. http://www.historyofcars-f.com/items/7923799724.html will get you one for $8.50. Covers most of the HiPerf Ford stuff, in a form you can stick in your shirt pocket when you go junkyarding or to swap meets. Steve Christ's book onrebuilding big-block Fords is a standard in this area, though I've found a couple of places where he was off a bit. Hard not to be. The casting numbers may or may not tell you anything, particularly on the newer cars.

The Medium Riser manifold is a nice item, and rarer than you let on. The heads that go with them are C5AE-R, and run 2.19 inch intake and 1.73 inch exhaust valves, and have substantially larger ports than the 390GT heads. 390GT has 2.02 intake and 1.55 exhaust valves. Still breathes okay - exhaust manifolds were the biggest restriction on that side. Intake manifold, of course, as well.

The aluminum manifold also weighs 50 lbs less. Look elsewhere for my Harley v. SS396 story for the light take on HP to weight. If youcan find some MR heads, that might be interesting. And a 1U crankshaft, which was originally Merc 410, but also used in the 428. Has almost a quarter inch longer stroke than the 390, and the 410 uses the 390 bore. If you bore .060 over (check the integrity of the block you get before trying this), you get close to the 428 dimensions (3.948 x 4.110 vs. 3.948 x 4.130).

I like the 390GT/428CJ cam for normal use. Mine pulls strong to about 6000 (a little over, really), and I'm running stock cam, Crane anti-pump up lifters, Crane springs, iron CJ high rise, and stock Holley 735.

Headers will help a lot, too.

I've got about $10k in my engine, but that was top of the line Bay Area machine shop, a new service short block, and $2500 to rebuild and vastly improve a stock set of C8OE-N 428CJ heads. I think I could do one for a LOT less, if I weren't worried about date codes, casting numbers, and so forth.

I've got a 390GT intake I might sell, but I'm guessing you could get one locally for less than the shipping to get one from Calif. I'd stick with the MR if you can find heads.

Maybe someone else has an opinion on the MR manifold on something like the Mustang GT heads with port work, or the 428CJ/427LR heads. - I take that back. I just looked in my pocket guide, and the port sizes for the MR and CobraJet manifolds are the same. 1.24 x 1.94 inches. All the cc sizes are in the pocket guide, too. Email me if you have a casting you want looked up, or get one of the books from someone like Tony D. Branda, or Ken's Cougars, or Mustangs Unlimited, or such.

Heck, if you're not going to use the MR, let me know. I might want it for my F100.