The big Whelen might make for a fun thumper. I know every time I see a 1917 bad thoughts roll thru my brain.
1917's are capable for more than that, my good friend. I am negotiating to get one in 585 Hubel Express! 700gr bullets, baby! My own 1917 is a wildcat 338/8mm RemMag.
Agreed that a 35 Whelen would be a good, fun thumper. But in a 1917 I would be inclined to go 358STA.
To the OP and original question, my suggestion is that since you got it at a great price, sell it and put the money into something you do not have and need like a micro varmint caliber a la 22Hornet or 222. At the other end there are lots of true big bores to play with, and you don't have any powerful over .40's. The list of probabilities there is long and varied.
