Reblasting of Aluminum Motorcycle Parts

I bought a basket case project 1973 BMW /5 motorcycle. The seller blasted the engine, tranny and related aluminum parts with sand. The result is a more etched finish than the desired original finish. I have been told to glass bead blast again and that will "peen" the surface to regain the smooth, original casting surface. The glass bead grit sizes are also confusing. Please advise.

Air pressure and gun angle have a good bit to play with the finish as well as duration.
The larger the bead, the wider the impact zone and normally the intensity of the impact.
Bead size goes by mesh size. 100 has 100 brass strands per linear inch. 600 has 600 strands and it is a powder to pass thru it.
Talk to whoever you will buy the bead from and they normally can tell you what the best choices are, or if not contact the bead OEM tech services. Consider having a professional shop do it for you. Unfortunately, that normally means larger cities than I live in.