Nice photos justin...night racing is pain in the arse to shoot, isn't it?
You might be limited by your camera, but you need to get that shutter speed up...or shoot off a tripod or monopod.
Don't get me wrong, it's a cool effect to have the road and wheels blurred, and those photos sell, but look in any of the racing mags at the type of photos they buy and you'll see what they're looking for.
As for the fence - you're on the wrong side!
I imagine your shooting from the stands as a fan...do you have a business website and letterhead? That and a professional look in person gets you credentials for the infield. You don't have to pay and you get a better view of everything!
I've been doing part time racing photography on and off for years - but it's been a while since I've done it. I shoot mostly open-wheel - fun stuff!
If you are serious about this...start selling as soon as you can. A lot of big time race organizations look for proof of publishing to weed out the fake freelancers from the real ones when giving out credentials. I've literally have had to bring the mags/book and show the photo credit to prove I was the real deal...