TarionzCousin
Second Most Angelic Devil Ever
In the past, my players have made an expedition to the Barrier Peaks. 

In general, I'd say that most D&D games already operate at a level of technology that is equivalent to the 19th century with a few odd gaps - such as the lack of steam engines or firearms. Most D&D players hold assumptions about the past that are the product of movies, and as such wildly underestimate how modern various tropes actually are.
For example, do your sailing ships have a 'crow's nest' where lookouts can spot land? Then your sailing technology is 19th century.
Or, to come at this in a different way, based on the costuming, social order, weapons, technology, and so forth most Disney 'Princess' movies are set in the 19th century and not the 13th.
Or to come at this in a different way, the Highland tartan kilt is 18th or 19th century garb. William Wallace would have never worn one, although he did at one point have a monk's tonsure.
My point is that the middle ages are so remote in the past, most people haven't a clue just how alien the world was and even if they did, don't limit themselves to that world. There is a good possibility that aside from the guns or steam engines, the trope D&D world is already the technologically advanced world you are looking. As such, as a practical matter, paddle wheel steamers, steam engine automobiles, early industrialization and so forth can be introduced without really worrying about rules for them, since the sort of things that they allow for are generally not things that DMs ever worry about anyway. I'd pretty much guarantee they'd have no practical impact on most peoples games.
Guns on the other hand, you'll need rules for, but my suspicion is that they are going to be an NPC only weapon - because a longbow in the hands of a PC is just going to be so much more effective for the PC up until the introduction of repeating weapons circa 1860 or so.
Does anyone have (or know of) rules for a non-magical motorbike in 3.5 D&D?