[ItBites]

Yours is a C4 - for sure, thanks for the picture, but your halfshafts should be aluminum and yours look like steel (like the C3 halfshafts) from the rusty appearance. I suspect your C4 IRS has been narrowed and the halfshafts replaced with steel ones, which may be good from a durability standpoint.

If it is narrowed, the spring is also shortened and if not made narrower, will have a wheel rate well in excess of the original vette it came from and then is compounded by being in a lighter car...

On mine (not narrowed), the Vette rate was too high for my lighter car, so I shaved the sides of the composite spring to reduce the rate. The rate is directly proportional to the width of the spring, so if you make it 10% narrower, you get 10% less spring rate. I shaved the springs with a band saw first (leaving the center and ends full width so the mounting is not altered) and then sanded smooth with a belt sander. Mine has been this way for over 15 years, so do not worry about if this somehow damages the spring. Do not alter the top or bottom of the spring (do not make it thinner) - only alter the width. This is also a one-way street, so do this process in small bites; there's no going back!

I also see your shocks are at a steeper angle, which will make them effectively softer (less control), but I have found that typical Vette shocks are also too stiff, partially because my wheel spring rates are down from Vette stuff, and partially because my Cobra is lighter. I also use the QA1 adjustables at the front and find that I only use 3 clicks for road racing and zero clicks for drag racing.

Vette Brakes is your best source and they have heard of this before because I have consulted them numerous times.