I understand. You will of course get much better and more effective patterns with Hevi-13 shells but if you want to use the factory lead-only choke that came with your gun, I'd recommend the highest lead payload shell with #6 shot that you can find.
I'm not a big fan of 3.5" shells however, so I'd recommend a 2 oz. load of #6 shot in a 3" shell. The Winchester "Red" shell, XX should work.
What will help your gun pattern better, regardless of choke or shell, is for you to "deep clean" the bore and the choke. that process takes a little bit of time but it's well worth the effort.
You can find the guidelines in the article "Cleaning a Shotgun" barrel by clicking on the allaboutshooting banner below this post.
Good luck this spring with your 835. They are great guns.
Thanks,
Clark