[Speedbumpauto]

If you take a small sharp chisel and start tapping at the spot under the sheet metal where the rivet head meets the sheet metal and at the same time start angling up on the chisel, those rivets will come out. Tapping under the sheet metal lets the sheet metal pull up kind of evenly on the rivet head. They have a little spiral thread on them and can be re-used with a touch of red Loctite when installing. That way you can blast all of the manifold and the only part you will have to worry about is the exhaust cross over where sand can hide. I would NOT do it unless the manifold has been hot tanked before hand. Depending on the medium you use, IMO, there won't be a problem with blasting the machined surfaces. I usually finish those surfaces with a jitterbug sander and 120 grit paper.