how large of a carb can perform well on stock 273 commando ?

Sorry for going off topic but I would like some info on the commando valve covers shown. I recently picked up a pair that require cleaning up and repainting. Was told by the seller it was probably wrinkle paint but niether they or those in pics look wrinkled. What is the proper finish?
Also would appreciate suggestions for cleaning up the aluminum fins. Have started with 220 grit paper and then progressing up with finer grits. It's
coming along but very slowly. Any ideas for speeding things up.
Sorry for butting in.
Thanks Bob