Im just going by memory that holden,fords and valiants had different springs for v8 and 6 cyl models due to engine weight differences , if you put v8 springs in your 6cyl car the ride would be firmer,but could be before all the modern whizz bang components came out to help things much more easily, i dont know jack rabbit about what parts you use to over come these obstacles obviously,im going back 20 years ago when you did things on the cheap.these days there is much more info and products to help with alsorts of mods.