The Rodgers 760 is a two-manual organ that has a fairly standard American Classic specification (Great, Swell, Pedal) with one exception. It has a Positive division that, if I remember correctly) is also playable from the Swell. The Positivities was meant to control two ranks of pipes, but you can use in Hauptwerk it since it generates MIDI signals.
It should be the case that you can obtain any three (or four) manual Hauptwerk sample set for a medium to large American Classic or British romantic organ and wire it up. You can assign a few stops from a Choir division to the Positive on your organ. I suggest using HW's Master Couplers to make your Positive a floating division that can couple to any manual and pedal. Also, download a MIDI monitor program and take a look at all your "extra" pistons (e.g. Flute them full, Main Chorus off...). Some of these might also generate MIDI stop signals and therefore can be used a stops or couplers in HW. You will likely have to make a few compromises and ignore a few HW stops - but this will get you up and running quickly.
You can then use the CODM capability to fully automize a sample set to your console. It is not too difficult. If you have any computer programming background, you should be able to use the CODM code fairly easily. HW comes with several good examples of CODM organs that you can use as examples.
There are also some HW sample set developers who can do this job for you - for a fee. Though I do this a lot for my own use, I am not looking for business myself.
Les