For me the pecking order, or desirabilty has to start with IRS. Been there with a 9" live axle, aint going backward. The SPF they landed is a good call. Roush 427 is a bit over the top for me, to big a number from a small block. I'd stop around 400 cubes or so. Not being a big fan of SPF or BDR myself, I'd consider other makes. Like MrMustangs ERA would be an excellent choice! Pretty much got it all.
What really has impressed me with my ERA is the LACK of "squeaks and rattles". My car is a very early one, #154, around 1986 or so build date. STILL an incredibly solid car. I'm comparing that to other Cobras I've been around or owned, it's just hard to beat an ERA, period.
Anytime you have a "pecking order list" it can get ugly. A lot of it comes from the heart, what YOU expect, what YOUR standards are, hard to put a finger on it.
Any replica Cobra outside the "stock" deminensions would be a no go for me. Longer, wider, nicer, OK, what ever, I prefer to stay closer to original specs in that regard. FE is of course a very desirable option in my book, with "side oiler" leading the pack in that regard. FIA style body with a small block would work out nicely. Daytona Coupe with a small block would also be very nice. GT-40 with a small block would be OK, with an FE would be terrific! I might do that one some day!
Not interested in Chevy or 385 series motors at all. NO auto trans, all though with age, if my knee's go out, I might have to revisit that issue.
While dual carbs are extra cool, I would seriously consider a single four WITH easily removable turkey pan option! Webers, hmm, thats a tough one, BIG money and concerns about the tuning and mpg would make me hesitate. 5 speed trans would be a plus ONLY if the gearing, rear end ratio and camshaft profile are all in nice harmony. PLUS any 5 speed HAS to have the forward facing gear shift linkage to appear like a top loader, otherwise, it's out. 16" rubber MAX size, would lean toward 15". Fuel injection? Wouldn't rule it out, but I would hesitate.
No matter WHAT you call it, the Shelby nameplate carries a great deal of weight for MOST people, hardcore or newbie, either way. It's a genuine Shelby product, which is pretty cool. Me? I dunno, I'm not sure I'd want to pay the extra bucks for the name, but I can understand those that do. I'd probably go Kirkham to save a few bucks. And then be all depressed when the CSX values slowly start to rise while the Kirkham value begins to fall.
And thats the way I'd call it...