Yeah, the adapters simply are a spacer that sets between the Trans and the bell housing and negate the need to trim the trans. Either method can work fine, just depends on which route you want to go. In my case I found it easier and cheaper to modify the trans. I've considered building an adapter myself just to do it but haven't gotten around to it.
I've got a list of the ID Tags on my site http://www.mongosgarage.com/tech/t5/T5tag.htm

Mongo


Mongo's Garage
Vintage GM Truck's & Parts
https://mongosgarage.com