Hey stgard,
the name of the seal is the "top rail seal".
As I understand it, there is no gas pedal cover. But some people use the clutch pedal cover (same size, so I've been told) If anyone knows different, please let me know.
A good place for parts is
www.victoriabritish.com ,there you can get a catalog to order almost every nut and bolt on you MGB or GT. The only thing that sucks about them is that they dont have an online catalog. Many people know of more places to get MG parts, but that is the place I'd start.
Have fun with your new MGB!!!