fatboyslim;
Is your donour car a Fiero? I am assuming so since you are talking about Held/Arrault. Making wider control arms is not that hard to do. I made my own wider tubular control arms for my old Ferrari 355 build. My fronts were 2" wider each side and the rears were 4" each side with coil overs in the rear. The big part is that you end up changing the suspension geometry a certain amount when you extend the control arms. This needs to be thought about seriously as I have learned over time. The wider control arms move the centre of moment of the frame under cornering conditions (up I think) so if you do extend your arms, go to a place where you can gradually ramp up the cornering speeds in safe conditions to confirm new handling characteristics before heading out to the mountain passes and dive into a corner. Wider control arms are not necessarily a bad thing but you just want to know the change in handling before getting aggressive as the pre88 Fieros already had inherent suspension idiosyncrasies from the factory. Adding more changes just adds to the uncertain reactions. if you have a pre88 Fiero donour, make sure you remove the rear bump steer as well in the suspension as that is a large part of the factory Fiero idiosyncrasies and helps with the new geometry handling.
The main reason for the coilovers on the rears of Fieros is to gain room behind the wider rim/tire combos used on replicas as the stock springs are quite wide on the Fiero. The strut remains and you just change out the springs. This also allows you to select a different spring rate.
Adjusting the ride height with coilovers is also a common practice but it ends up removing shock travel in the compression direction so you have an increased rick of bottoming out the shocks which wears them out fairly quickly or out and out breaks them if you hit hard enough. You can use shorter struts when wanting to lower the stance of the car but that still changes the geometry of the lower control arm on the rear suspension because the control arm pivots are lowered at resting stance therefore changing the angle of the control arms. There are many different ways to address ride height and still get decent suspension performance and as many different opinions on which ones work best....
In a possible future Fiero build, I will be lowering the car by moving the control arm mounts up with shorter struts rather than use the coilovers to lower the stance.
As for the width, another item to address into the solution is the length of the axles. if you are staying with transverse engine/trans setup, you will end up with a long passenger axle unless you add in an intermediate shaft. These can be found on many cars depending on what transmission you plan to use. Don't try to run the passenger axle the full length of teh new wider track.
My thoughts only and not looking for a flame war.
Cheers
Don
