· But Mad North-Northwest
I'm not sure that makes sense? A rear anti roll bar would increase oversteer, not decrease it.At the risk of going off on a tangent I will try to explain why the 1750 got a rear antiroll bar and will end with a suggestion. This comes from a talk with Max at Alfaholics. During the 60's Alfa was racing the GTV/GTA in competition. One of the problems was that the rear top pickup point is a little too high and it was negatively affecting roll centers. It was about impossible to change the pickup point on the differential, but they could change the front uprights to improve geometry. When they did this for street cars it caused the cars to oversteer and thus they added a rear sway/antiroll bar.
Anyway, in the absence of other issues like sagging I'd base spring replacement on whether they look solid or not. I would suggest poly for the trunnion conical bushings and washers. Based on my recent experience I'd also suggest poly or heavy duty rubber for the trailing arms.
When I got my '91 Spider nearly 20 years ago the trailing arm bushings were worn out. My mechanic at the time replaced them with polyurethane in front and HD rubber in the rear of the arm, saying that the stiffer bushings gave better handling. A few months ago it was time to replace them again...