NEF's come with a trigger extension. Or at least they should. If not, they are cheap, like $7 online.
The height of the rings will depend on the scope's dimentions at the occular. Some are wider than others. It will also depend on the position of the scope forward or back depending on eye relief or personal preferences.
I have an NEF in .17hmr, and I used the Leupold (rifleman?) High rings, the ones sold at Wal-Mart for $13. Those works perfectly with a Simmons ATV, which is dimentionally similar to the WTC, but with a 40mm objective. This is a larger sized scope (but not massive like some varmint or tactical scopes).
Another scope/ring combo that works is the Burris FFII 3-9x 40mm, along with High Burris Zee Rings (Burris rings typically measure lower than other brands).
Your best bet it to go to the Graybeard NEF forums and directly ask which rings would be best by telling them which scope is intended to be used. Out of all the guru's there, you are almost guaranteed to find someone who has the exact scope and has mounted it to the NEF in a way where it clears the hammer, but also stays as low to the bore as possible.
Otherwise, try your best to guestimate before buying from a place with a good return policy, or find a gunshop that is willing to have you place the rings on the NEF and lay the scope ontop of them without torqing anything down....some shops will do this. Rings will cost more there, but you're paying for the customer service.