Crankset compatibility-slightly different version
 

I need to put a new crankset on a mtn bike frame that has been converted to a 'cross bike of sorts. I was thinking of putting on a compact double to replace the triple, I have bar end shifters with the front D being all friction. Is there double bottom bracket spindles that work with a mtn bike shell width and will there be compatibilty issues with the front D eventhough it is shifted by friction (not indexed)?