Caution with respect to the Stock Car bulletin is warrented. There are several reprinted in the DC Oval Track book (P4286727) but the focus was definately circle track. In many chapters they specify "Super speedway", "Grand national" or "Short track" recommendations. The only area I can help with is the "Handling Line".

The "Neutral Line" also appears in Mike Martin's book. (see "Suggested Reading for Handling") But it appears to be the same as the one emperically derived from short track cars (see: DC tech bulletin 141 "Basic Chassis Setup for Short Ovals). It is my conclusion that the concept is useful but the exact position of the line is not (except for the specific racing it was made for).

My conclusion is based on (a) the weights, spring rates and anti-roll numbers published for production Barracudas (A & E), and (b) my own and other mopax set ups for competition (mostly autocross). In summary, the slope is appears to be universal, but must be shifted left or right depending on the application. Details on my Neutral Line page.

I can not help as to where to get t-bars larger than 1.24, but obviously they were available for circle track at one time. (The sources listed in Martin's book were dead ends 15 years ago.) However, it is true that Firm Feel is making their torsion bars in-house.

I've never seen the tech specs on the Chrysler France race cars. The photos show a lot of body motion compared to the US trans-am prepared cars. This may be due to rules or other limitations, or the need to compete in hill climbs and other open road events where a reasonable degree of off-pavement performance and ground clearance was needed.

As far as 230# leaf springs go, that should not be too hard to find. Either of the big two circle track spring companies shpuld be able to make up a set. This may be the cheapest for testing rates and arch etc. Eaton will of course be willing to make up a more sophisticated stock type spring pack (6-7 leaf) with a primary and secondary leaf of the thicknesses, shape, for your needs and a final ratio and rate you want.