If an aftermarket part meeting all the criteria of the replacement rule for material and dimension can be found or made then it is legal.

Merry christmas to you all.
[/b]
So........

The valve springs I just picked out are made of steel and have the same exact dimensions as the OEM springs. They happen to have twice the seat pressure. Legal? I think not.

While the manufactured part may not have a physical aspect that is as easy to measure as spring pressure, if it doesn't have all the same characteristics then it is illegal.

If the stock uprights are cast pieces then it is illegal to replace them with parts machined from billet (a solid block of material). If the stockers are steel, then it is illegal to replace them with aluminum, or, a higher grade steel.

My money is on the stockers not being billet pieces. And, if they aren't then replacing them with billet pieces is going to have someone writing some paper up over your car.

But, these are just my opinions and I'm sure other opinions will vary.