You'd probably be better off asking this in the Mechanics forum... not that mechanical ability is lacking here.

There's no real functional difference between "road" and "mountain" cranksets. The only real issue might come when you need to choose a front derailleur. The choice will depend on which crank, which shift levers, and what frame they're going on.

The 105 and RX100 groups didn't get triple cranks until 1992. Before that, the only way to set up a low-geared touring bike like the Sirrus was to use "mountain" parts.