In the very early days of the Radial challange it was not so much that way. You had to use the standard carb until the mid 70s, and the drive train had to be from the model used. Later on it got kind of wild, closer to SCCA GT rules. As matter of fact I converted Bobby Archers championship Alliance to GT-4 by moving the fuel cell.
The point is that those modifications have been used much earlier than you might guess, and don't in some cases have to cost a fortune to do.
In a Pinto with a single lower control arm you can eliminate the compliance of the inner rubber bushing, and gain the negative chamber you need by simply cutting off the end of the arm, welding in a nut, and screwing in a Heim joint. The whole thing costs about $20 compared to the cost of hard bushings, legal ones, and offset bushings/chamber plates on newer cars.
I am not suggesting that we do that, but to some, weighing $20 against $150 per side is tempting, and some can justify to themselves that it makes no competitive difference.
If I am allowed to spend all the money in the world to legally adjust my chamber does it really make it more fair for me to spend the money to do it that way as opposed to doing the same thing on the cheap, not currently allowed by our rules?
Is that why I have seen several Honda CRX rear upper links that have been cut and welded shorter? They have negative chamber for next to nothing cost wise as opposed to buying the high priced parts from someone's sponser.
Maybe we should just think about what the wording of some of our rules means and what it does cost wise. If it is an allowable mod, then the methodology in many cases only lines someones pocket.
I still like the first list.