I have neon injectors, only noticeable thing is a better throttle response. Didn't notice any more "power"
Most go with S10 springs for a bastard pack. dodge van may be too stiff.
I swapped my cluster and had to change oil pressure and temp sensor. In my case, my stock cluster had lower miles (85K) then the replacement (137K). Basically, I'm actually 50K lower than the new cluster. FWIW, I took a sharpie and marked on the back of the new cluster with the old cluster mileage, the current mileage on the new cluster and the date. That way if I ever needed to reference it in the future, I know where to find it. Just my OCD.