Hi Collin
My recommendation to you would be to approach a company who do "sim rides" for the public in actual flight simulators. I'm pretty sure there is a company who do this in Cranebank (the British Airways training centre) for example, but as you are looking for the analogue engine gauges, its probably worth contacting Lufthansa as they have this layout on all their 737 classic fleet to my knowledge.
I'm not sure if you are aware but the flight simulators used to train airline pilots have the real switches and cockpit instruments, also noises like battery relays, generator switch overs, starter cut-outs etc are very authentic so I think it would be much easier for you to get the photos and recordings yourself this way rather than trying to gain access to an actual aircraft or relying on someone else to do the work for you.
Good luck, hope to see your product on the market in the future.