Why would you lower the back?
Not for looks i guess? and if anything to improve handling, ive read making the back ever so slightly higher improves handing.
Anyhow, your 54 diameter podfilters. I've got those fitted to my bike aswell. I used the tubes from my og airfilter to connect em to my carbs. I suggest you have a look at my page project page, where you can see how i made my 54mm podfilters connect to my carbs.