Trying to polish engine fins would, I think, be a nightmare of labor. Repainting would be preferable. Surface prep is the key to a good job. When I restored my 750 I used a gravity feed soda blaster I bought from Harbor freight. Again, prep of the part is critical. All grease and oil should be removed before blasting. Soda blasting has a benefit over vapor blasting in that it will strip old paint quickly and leave the surface slightly rougher than vapor blasting and is a very good surface for paint to adhere.
Vapor blasting is another option. It will leave the surface with a more sheen like look than soda blasting and can be top coated with a high temp clear coat.
If the engine is disassembled during the blasting, it is absolutly critical to have the parts cleaned and every nook, crannie and passage physically brushed out several times between rinses and high pressure air blown down each passage. Any blind holes need to have an air tube stuck down to the bottom of the hole and then blown out. Water will disolve the soda blasting media. Vapor blasting uses glass beads and the glass beads have an affinity to adhear to any oil/grease so solvents should be injected down holes with brushing to chase the holes. You do not want ANY glass beads inside the engine after reassembly!
-P.
