[Vwdiesel] sandpaper for lapping

[Libbybapa at wmconnect.com]

I have used sandpaper on a flat successfully for many surfaces.  I would like 
to use them on an exhaust manifold and potentially a head.  Does anyone have 
a decent source for larger sticky sandpaper? say rolls of 320 or 400 psa 
(sticky) paper 12" wide and however long?  Any other recommends?