Lowering springs are the worst invention ever coil overs is the only way! Take the arb off ya don't need it 
why would you get is of the arb???
People uprate them for a reason!
Fair enough if it is a show only car but on the road it is a idiotic idea...
Ignore Danny, he likes to pretend he's in the fast & the furious so loves losing control of his car and making the tyres squeal...impresses the young girls apparently
To be fair, his car is so low that the arb will be making little difference.
Back on topic, don't get lowering springs, you'll end up buying coilovers eventually anyway so it will be a false economy. You'll manage ~50mm drop before hitting arb issues, that can be resolved easily enough with an arb that goes under the driveshaft instead.
As for spacers I'm running 15mm front and 20mm, neither bolt on, but both hubcentric. I'd look at getting them from JJC:
http://www.jjcraceandrally.com/
