If you swap to a RR chassis, you are losing the Sj's best asset, lightness, coil conversions can be got quite easily and will give whatever lift you want,engine wise i personally would go for a 1.7 izuzu turbo diesel as fitted to some astra vans etc, combine this with a 2l carlton 5 speed box and you would be amazed at the difference, skys the limit with modding Zuk's, money makes it easier put it that way :D