I've been enamoured with a lever action as a suppressor host for a while now. I thought 38/357 would be good. Then I looked at 45 Colt. When the velocity is capped, heavier bullets are the only way to get more power.
Also, the 45 Colt rifles just shoot 45 Colt. There isn't a question of a 357 or 44 magnum rifle not running 38/44 special rounds. I understand it's rare, but still. Heavy bullets up to 300 grain, no worries about shorter ammo compatibility, naturally subsonic...45 Colt seems the likely choice. The only issue is 357/38 and 44 ammo used to be more common. Not now though.