Yep. Go have a look on page 145.
There are four basic sources of units. Production, Purchase, Salvage, and Legacy. Clan Trials for units sit somewhere between purchase and salvage. So you will start with the units built by your faction. Then you look at what you have had access to historically. For the Clans that often means Star League vintage units. In the case of the Dominion, Pumas and Demons were being built by ComStar in the 3060s Free Rasalhague Republic rump state. Skulkers, LRM Carriers, and APCs were built by the old FRR, they basically went out of production in the 3070s but could still be found in low end forces. Now there are modern Clan versions available.
Salvage, you look at what the neighbours are using and claim some. Purchase, is a good way to get some wierd out of place stuff into your force. Usually that means looking at what Clan Sea Fox has access to, but the old MechWarrior Dark Age game left some oddities available like the Kinnol.
Probably most importantly don't stress. There is no right answer. The Dominion is actually pretty easy because it has some consistent favourites that last back to TRO3050. The FRR favourites might even come back depending on how things play out as the writers go back through TRO3055 and 3058. I know that is confusing, but it will make sense one day.
Start with the Dominions Divided RATs. Use the most common units as your skeleton. The flesh it out with whatever you like.
