Looks like you have a bit of work yet before you will be ready to put an improved suspension to good use from the pictures you posted. Remember the air box supports the back of the carbs on this bike so if you decide to go with Uni foam filters, you may want to switch to the shorter rubber manifolds or look at making a small support bracket for the back of the carbs. The original side covers were ABS and broke easily. They are no longer available from Suzuki but there are a couple of people offering reproductions these days. The PEI cover is available off ebay unless you got it with the bike?