Shimano Bar end shifters make kind of awkward downtube shifters. I like something a bit longer, without that odd kink in them. If you don't want indexing, downtube shifters are dirt cheap, I would buy something purpose built.

Plus, at a later date, you can mount your fancy new downtube shifters to the bar end shifter pod and have really snazzy bar end shifters. It works for a surprisingly large number of shifters, if you're willing to kludge a bit.