If you haven't already, the progressive rate springs at www.v-classics.com
are quite well spoken of. I seem to recall that GRM used a set and were very pleased.

Stickies on wider 14" wheels will help you put the power down a lot (look at Fords for rims)! The difficult part will be controlling inside rear wheel lift (and subsequent spin). Be careful here as the loss of traction coupled with sudden "hook-up" is the recipie for breaking axles.

You will be propelled into "prepared" under the SCCA system for coil-overs and the competition there is fierce. I think there is a lot you can do to what you already have before coil-overs become beneficial.

Getting the "Whoa" in hand can help lap times too. Invest in braided teflon brake lines and high quality (like greenstuff) brake pads. Rears could use some help in the biasing department for serious stopping but are OK in stock form for all but all-out efforts.

G'luck,

Mike!