You well-know the second show he was featured in, the Tony-winning and Pulitzer Prize-winning 1776. But the first musical is far-lesser known, Ben Franklin in Paris, which opened in 1964. The show followed Franklin's efforts to raise money in France for the American Revolution, and it certainly had a major star in the role, none other than Robert Preston. And though it wasn't successful, it nonetheless ran for a moderately respectable 215 performances.
I'm not crazy about the by Sidney Michaels, though it had a few very nice songs. And one of them, happily is actually available on video. Not great quality but very watchable. It is likely from a performance on The Ed Sullivan Show (to bring Ed up again...) and includes the scene that leads into the song -- "Half the Battle."
The other song from the show that I like a lot is "Look for Small Pleasures." It's audio only from the original cast only, but well-worth including here. Here is Robert Preston and the female lead Ulla Sallert