It is indeed a generous deed to donate such a collection. Nevertheless, unless you have an accurate appraisal and can use current tax benefit, have you considered alternatives to an actual donation?
My immediate concern would be the sustainability of the museum. Does it have an adequate endowment or source of funding to assure longivity?
I offer this question merely in suggestion that you might want to consider a loan, or at least place some reversionary contingencies should the institution fail.
It is difficult to offer suggestions on arranging the display without the benefit of examining the collection and the museums's facilities.
Obviously you will want to make best advantage of lighting arrangements and this is often attained by using some back draping of contrasting colors. You need to decide if you want to categorize the collection by era, railroad, geographic area of Tx. or similarities of the items.
Consider the environment. If the items will be displayed in a dusty location, recognize that regular cleaning will probably be required so consider access to the items. Obviously, don't overlook security.
I'd recommend that you take some time to visit some museums. If there are no railroad museums in the area, check for historical societies, and even art galleries if needed. Don't overlook colleges or universities, as they often have collections of archeology etc.
If all else fails, visit some retail stores such as gift shops, jewelry stores etc. Observe how their showcased wares are presented.
Again, it is great that you are sharing your collection, and I am sure that you will feel pride that others will benefit from your endeavors.
Finally, get some media publicity and don't hesitate to visit frequently and be a curator.