Your car looks great! I like the look as well, as long as it works, who cares what it looks like
You should definitely get some instrumentation. You might not be able to use a Scangauge, but as long as the engine is fuel injected, you'll be able to use an MPGuino, which is just as good for older cars.
It looks like your car has a CD of .33 (
source), which is pretty good, and with your mods, you've definitely lowered it. So, aerodynamically, I think you're doing great, now with some instrumentation, I think you'll be able to notice even greater improvements.