I Did A Little Research, If'n Anyone Cares...
Most piston rings are cast iron (this may be pretty common knowledge)... What may not be common knowledge is the fact that there are differing versions of cast rings including alloy iron, ductile iron and some other stuff can't remember. Anyway, these are common and pretty inexpensive.
Then there are chrome plated cast iron rings or "chrome" rings. These are said to perform a little better than the cast iron as they reduce chamber wall scoring. However, they evidently aren't especially long lived. Now what constitutes a long life I don't know, so they may actually be fine for your application, but I can't make any recommendation.
Now, what I wasn't aware of is that most passenger car rings are moly rings. So these are not rare or especially expensive. What makes them different/better is that the grooved oil ring is filled with moly (the groove that is). Moly will absorb oil and will reduce chamber wall friction and scoring while establishing good hydrostatic seal.
Therefore, it appears that the moly ring set would be the best bet and it may just be an OEM replacement set.
BTW: In my earlier reply I was mistaken... I found no mention, in any of the articles I read, of an incompatability of any of these rings and any fuels or any seal deficiencies. It seems that the differences have mostly to do with friction, chamber wall scoring and ring life.