Lightroom Keyword Database sorting

I have a huge database of transport museum/car show photographs.

I keyword all photos by manufacturer, model, year, etc.

The only way I have found to produce a slideshow that displays all of a particular model of a car by year is to maintain the Title Field with the year of manufacture and manually sort the slideshow by displaying the title in the Grid View and sliding the photos around, (which "crashes" every 40 or so shifts meaning restarting the database).

So when I choose something like Ford Mustang which produces 300+ Mustangs to shuffle, it takes quite some time to reorganise. I save the slide show, so when I go to the next car show and add another 20 or so Mustangs, I then at least have a head start to manually shuffling them back into the slideshow in the correct places.

It would be really great to have a single numerical field in the database - in my case always the title field - that I could tell the filters to sort by, which would save me hours of work