Tim,
I think your going to find your time driving this car, is in the "top" of your behind the wheel experiences. I owe it to Ken Gray for giving me a ride in his Series 2, back in Chico in the early "80's. My ownership of a Series 1, serial number 509 lasted for 6 years. Being located in Carmel Valley at the time gave me access to the roads the car was meant to be enjoyed on.
The stock springs are going to be a challenge. From your picture the squat at the rear, under acceleration is a reflection of their less than 100 lb. spring rate. How you address this will be the key. I did get the chance to auto cross mine on a number of occasions. I never did scrape the door handles, but I did get close according to those at the events. That and driving on Pirelli 145 SR 13's teaches you to work with trailing throttle oversteer. Then there's the camber changes at the drop of the throttle, from both ends!
David