Hi-
I spent a ton of time researching competition car dash layouts and gauge availability about a year ago. My conclusion was that if you want the authentic and correct gauges, you should source them used or new-old-stock off of eBay. The current offerings from Stewart-Warner are not accurate copies, particularly the speedo and the fuel pressure gauge. As already noted by Allen immediately above, the Jones 4" tach (which I put in my car but never saw in an original) can be ordered from Pegasus, but remember that it is a mechanical drive tach, which means you will also need to source a tach drive distributor, not the easiest thing to do; I got mine from Mallory, not cheap.
For the 16 factory FIA/USRRC competition cars built in 1964 and 1965 with "cutback doors", there were at least three different dash layouts.
The first five or so cars had what has come to be called the "FIA dash". It looked like this (from CSX 2345). This car appears to have a Smiths tach, which you'll need to source used if you are a stickler as the reproduction isn't quite the same, although it is pretty close. Some of these cars had the Sun tach, which is now available in an accurate reproduction:
Another batch of cars had a slightly different layout, which some call the "USRRC dash". Below is CSX 2431, also with a Smiths tach. Both this and the "FIA dash" had the same line-up of five 2 5/8" S-W gauges, just in a different placement.
The last of the FIA/USRRC style cars produced had the dash shown below, which I copied in my car. It has the advantage of the speedo where you can see it, and a glove box (where we placed a fuel level gauge). As you can see, the small gauges are all S-W with four 2 5/8" in diameter and one 2 1/16" (the ammeter):
From CSX 2557 with a Smiths tach:
From CSX 2558 with a S-W tach (this tach is also available as a reproduction):
This dash below is from a customer ordered car, CSX 2514, and is a slightly modified "street" dash. The small gauge cluster is made up of five 2 1/16" gauges and a 2 5/8" fuel pressure gauge, which replaced the clock. All were S-W guages:
Earlier competition cars used mostly Smiths gauges with a Sun tach, a S-W ammeter and a S-W fuel pressure gauge. Below is the dash of CSX 2129, which was one the 1963 "Sebring" race cars (the 1963 "LeMans replica" Cobras had a similar dash). There are four smaller Smiths gauges that are 2 1/16" in diameter, a S-W ammeter gauge that is 2 1/16" in diameter, and a S-W fuel pressure gauge of 2 5/8", the same as in all the other dashes pictured in this post:
BTW, there is a vintage Smiths tach on eBay, but it is expensive and not quite the same as what was used in the Cobras:
http://cgi.ebay.com/ebaymotors/SMITH...Q5fAccessories
Hope this helps!