What seat base for Sparco
Do you need fore/aft adjustability, are you the only driver??
If not, you can get the Sparco side mounts (which I believe you MUST use anyway with that seat, since it is a side mount ONLY model, with NO provision for bottom mounting, unless they changed that recently?), and mount it directly to the floor (with reinforcement plates on the bolts UNDER the car).
If you are that tall, this may be your only choice anyway, as mounting side mounts to a base can raise things up fairly high towards the roof (especially if you mount them to sliders first).


