"Cool! So I can make it so that only certain weapon types can use certain mounts. Is there any way to get the computer to select these mounts? "
Yes, Fyron is right, the AI will use the Last mount in the listing. But this also means you can get creative to 'force' the AI to use certain mounts.
Ways to do this are multiple listings of mounts (ie, you have 3 engine mounts but want the AI to use a specific one all the time, just simply list another identical mount at the end of the file with an 'AI only' txt tag...) and the use of the min/max tonnage settings. I've got my mount modd set for destroyers to use Extended Range mounts, Cruisers to use Pulsed Mounts, all AI ships to use Military Engine Mounts (except crystalline or organic races which use their own engine mounts which can be implemented by the use of the tech required fields...) and all ships use the shield mounts according to class except the crystalline races which have thier own shield mounts.
AI units will also use shield mounts for fighters and high density armor mounts for the troops as well.
any other questions.....

(oh, and here is a freebee, mounts cannot affect the seeker of the missile weapon....ie, no extra damage etc....but they can affect the size/cost/supplies etc of the launcher....range can be changed for the firing of the seeker {when it is actually fired} but not the actual range of the seeker itself, ie, you can set it to fire when the range is down to 5 but if the range of the actual seeker is 12 it will still go to 12, eliminates the 'missile dance'...)