Blasting it with the appropriate media will not pit it or erode the surface. Using an aggressive media or grit size definitely can though.
Walnut shells or a fine glass bead will give it a very nice finish. If blasting make sure its fully disassembled and cleaned very well before reassembling.
Last summer I blasted my intake, dog house and valve covers with a fine glass bead and turned out great. Looks like a new cast aluminum finish