Driveshaft Shop in N.Y.C.?

Me thinks my driveshaft may be out of balance. I get a nasty vibration at about 3,500-4,000 RPM. I have the correct dampener & flywheel on my 360.... new U-joints....scattersheild is aligned.... mounts are good.

Question is, is there a reputable shop out here on Long Island that can balance my shaft? I'm not really looking to have one made unless it's absolutely neccessary.

Thanks guys!