OP,
X Mark/X Mark Pro trigger group parts are NOT interchangeable w/ M.Walker design(pre2006) 40X/700/Seven trigger groups.
A 40X single shot 3 lever 2oz trigger group does NOT have a safety lever option.
Remington will not sell trigger group parts to a non FFL.
Rifle Basix manufactures a 700/40X Repeater trigger group safety lever kit -$40USD.
OP,
As you learned the hard way by breaking the safety lever-
Apply the safety to SAFE
Tap the aft trigger group pin out from Rt to Lt
Take safety lever to fire
remove the bolt stop & torsion spring
remove the fwd trigger group pin
I've precision TIG welded hundreds of broken 700/40X Safety levers over the years.