The legacy versions you mention ALL come with 64Bit versions so if you transfer your plugs to your new account you should get the 64bit versions by default… you’ve paid for the plugins already so as far as i’m aware you SHOULD be able to use them with the UAD2… the updated versions of the plugins you mention are completely different versions, i think you’re getting the wrong end of the stick possibly here…
i have the original UAD fairchild which runs on both the uad1 and uad2 platforms and that comes in 32 and 64bit flavours… as do ALL UAD2 plugins…
so… if you install BOTH cards in your current machine and assign them both to the same system in your UA account now or before you put it in your new rig, when you transfer the UAD2 to your new machine you’ll be golden innit!!! 
If you’re still unsure why not contact UA support…
hth