With my Victory/Triomphe setup, I use 52/42t chainrings and a 13-28t 7 speed cogset, which gets me below 40 gear inches. Personally, I would change out the rear cluster first before replacing the ring. You might be able to go as big as 30t in the rear, I'm not sure. My Victory rear mech works great with my freewheel.
https://www.bikecalc.com/gear_inches