without sounding rude, have you looked at other cars as well, 4 years seems an awefully long time to save up, was just thinknig you could start having fun in something sooner for less money. a lot of us worked up to the zed and had some craking cars which are just as good fun.
as an example i had an MR2 roadster, mid engine, rear wheel drive, uk cars had LSD's half the power of the zed but also about half the weight as well. and you could do a turbo conversion on it for about £2.5k and push nearly 300bhp with out major reworking to the engine. mods were cheap as a basic car it wasn't a bad shape but with a kit on the roadster it could look very mean. i'll post up a pic of my old one if your interested. you can pick one up easily for less than £4k and they are awesome fun to drive.
i suggested this as i feel bad that your not having some rear wheel action yet, and i'm sure others might have suggestions