I am working with a Radical dealer to sell their out their New Old Stock (NOS) inventory and found a set of brand new Uprights that will fit Prosport / PR6 / SR1 / SR4 cars. To the best of my knowledge these parts are no longer available through Radical so this is a great chance to get some new uprights.
Update: Three of the uprights have been sold so I only have one Front LH Upright left.
Here are the part numbers and prices:
1) SU0036 – Front LH upright (1 available) – $900.90