First off, welcome to the Forum! Lot's of great folks here and lot's of great knowledge and advise, hope you enjoy it here.
I guess what kind of pheasant hunting? Wild or pen raised? With or without dogs (pointer or flushers)? Chokes for pheasants can run the gambit depending on how you hunt and where. Perhaps if you can give some details, it would help. A general rule for most upland birds is IC/Mod (.010/.020), but that can vary, all depends.
As to tubing, heck it's your gun, do with her what you like. I think tubes can be a real bonus. A Browning BSS is not a vintage Brit gun, so if you want choke tubes, go for it.
You may want to check these folks out:
http://www.colonialarms.com/Again, Welcome and Good Luck!
Greg