Mate, I love the XR7s and the '67s in particular have those screw in ribs in front of the rear wheel arches that look like claw marks... 
I think I'm pretty sold on the Summit 600 which as you point out is a Holley 4010 / Autolite 4100 knock-off with a few improvements. Seeing as how quite a few people swear the 4100 is still the carby of choice for small block Fords I figure you can't go too far wrong with a modern copy of it.
Still not sure on the intake - there aren't any cheap Weiand 8020's that I can find out here and it is a higher rise manifold than the 8124 isn't it? I am planning to add a 1" phenolic spacer into the mix so it may be better to stick with a low rise manifold.
As for the Weiand 8124 vs. Eddy Performer debate, everyone has their favourite but one thing that's supposed to be pretty consistent in dyno comparisons of the two is the 8124 produces a few HP more than the Eddy across the entire rev range. That and the fact that it's also a bit cheaper is swaying me more in favour of the 8124 at the moment.
INTAKE
there is absolutely nothing wrong with a performer intake for your app . i mean ZERO, NADA, ZILCH
Do NOT go solely by dyno results . i have been doing this for 40 years as a living, not part time as a hobbyist, so i have seen it all and then some . if you had ever been in a 271 hi po mustang with that similar crappy little intake, you would not even consider a stealth.
as far as running a stealth on it, yes it will perform ok but you will in fact have more bottom end with the eddy with a spacer . the difference will not be huge and some people are willing to give up a little power in the rpm range they want it in to have something that looks a bit more racey and cool and there is ZERO wrong with that . so these are the facts and you can use them to make your decision . i personally think the eddy performer looks like crap, but imo, it is still the best intake for your app, but again, the difference won't be huge.
if you want a medium rise intake, i would get the summit stage I or the weiand street warrior . they are the same height which is slightly shorter than the stealth.
GEARING
I am going to tell you the same thing i tell everyone which is the exact same thing that GENNN and boofhead and shaunp and every other knowledgeable builder will tell you, and it is this . if you want quicker acceleration, install numerically higher gears, or a bigger engine or a supercharger or nitrous.
the 271 hi po engines haul ass with the puny little intake, but the only reason they haul ass is because of the gears they come with . the standard gear for those is 3.50 . you can NOT special order a 271 with numerically lower gears because it will be a pig off the line so ford figures if you want numerically lower gears, you should just order the standard 4 barrel.
unless you have ghetto size tires, the best overall gearing for moderate performance without making it rev fairly high on the highway is 3.25 and every knowledgeable person will tell you this also.
CARBURETOR
as far as the rebuilt summit carb vs the new summit carb goes, i would take the rebuilt one due to the cost PLUS, they go thru and fix anything that was wrong with it so you know the thing is most likely going to be perfect . the problems are sometimes just metal shavings that didn't get cleaned out and got stuck in a port etc.
SPACER
You do not need a 1" spacer on a high rise for your app because it has sufficient plenum area. you can simply buy a 5 mm thick paper gasket or 5 mm phenolic spacer to help insulate the carb from heat.
EXHAUST
If the exhaust is stock, you will gain a little power with headers . if you want headers, the short style are fine and easier to deal with sometimes than the long ones . if you don't like headers, you can buy copies of the original 271 hi po exhaust.
