Rocketman, the 450/400 3" is the Jeffery case which has the thick rim. The 3 1/4 has the .040 rim. What rifling type does your rifle have? If it is Henry type, you will probably do best with jacketed bullets if the bores are rough. If you try lead only, be sure they have plenty of lube, and are fairly hard. I have not had good luck with PP and rough bores with Henry rifling.
All the best, Mal