The D7 Pathfinder is interesting because it has Excelsiors own 250cc ohv engine. That is the only part which you may have some difficulty finding enough information. Not that you need a great deal.
Otherwise the bike is as most Excelsior of the period, made up of proprietary components. Burman gearbox, Lucas coil ignition and electrics, Amal carburettor, Webb forks and so on. Rarely did pre war manufacturers like Excelsior ever do a modern full workshop manual style of thing. They expected the component suppliers to provide what you seek.
So, who you want is the VMCC library. Not only can they provide copies of much of what you are after they even have a 1933-34 Excelsior all model instruction book plus a 1934 catalogue listed. BMS used to do much the same thing but they were bought by the NMM and haven't had much of a website to check out since then. They might have it but you'll have to work to get it off them.
Finally, you may even have the de luxe version, the DE7 Chieftain. Much the same bike but with more chrome and tube girder forks. Not Webb pressed steel.
Lots of luck, it's an interesting bike of which few survive.
Cheers,