I recently bought a couple of 180 mm cranks on eBay to use with a Cannondale ST600 rebuild. The price was right, so I bought both without a specific plan in mind. One is a Specialized (flag) triple crankset with rings, and the other is Shimano Deore FC-M730 cranks, without rings. Both sets are 110/74 BCD. Central Pennsylvania is pretty hilly, so having a low gear option is important.

I've been reading about the popularity of compact cranksets, but don't see many (any?) vintage rings in 50T and 34T. I see that Specialites TA chain rings come in many sizes, but they're fairly expensive.

Is there any reason I couldn't put just two rings on the Shimano and use it as a compact double? Is there anything about newer 5 bolt chain rings that makes them incompatible with older cranks? For instance, I found the Shimano Tiagra FC-4550-S rings at a decent price. They are silver, which I want, but they look a little different from the typical "flat plate" chain rings of older vintage.

Recommendations and advice appreciated!

Thanks,
Don