If it was certified, then it wouldn't need to be recertified after time. However, somebody correct me if I'm wrong, but Lakewood bellhousings are not SFI Certified, merely SFI approved. This is kind of misleading, but I don't think they actually meet the SFI testing. The SFI testing requires that the bellhousing be able to contain all fragments which the LW can't do because of the starter opening. The SFI testing is actually done without the starter in place. Seems kind of weird, but I'm pretty sure this is how it works. Tech officials generally won't give you a hard time about this though since the LW is better than the cast aluminum BH. At any rate, sandblasting won't affect the strength. When repainting, I'd repaint it the same red color since this is how the officials identify it without crawling under the car to look for the sticker. Also try to preserve the sticker if possible. A blanket is not legal for manual transmission use, only for automatics. Also, if you're truly trying to meet the SFI requirements and you're below that 11.99 barrier, you'll also need a billet SFI flywheel and SFI rated clutch assembly. The SFI rated clutches are few (McCleod and Ram are two I know of).
Good luck.
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Jeff Chambers
T/S #4
12.40 Seconds/109.5 MPH
http://www.kellnet.com/chambers/default.htm