With gas mobile home units there is basically a standard 80 and a high efficiency 95/96 model... as far as oil furnaces, you have even less options when it comes to efficiency with Oil and Manufactured homes (at least at my local suppliers - yours may differ) I believe there are 2 oil options and the highest is 85%... as for brands, like a previous poster said, you have few brands to choose from - Nortek / Miller and Revolv and ThermoPride.
I personally have never done or even seen a heat pump / oil dual-fuel on a mobile home unit (and we work on a lot of mobile home units), but it should be doable. But before you venture down that road I would talk to your local supplier of whichever brand you decide to go with, to see if they have any recommendations.
Usually when working with any furnace in a mobile home, there is an option for a coil box already in the furnace to slide in a coil (or you can get them without the coil box if you are going straight heat - dont recommend going with no coil box then using a different cased coil unless its electric furnace)... But in any scenario, the coil doesn't come with the furnace. You buy the coil separately and you slide it into cabinet. (again this is true for what we sell - your experience may differ)
I recommend getting your coil from the same supplier you are getting the furnace from, so it all matches up and fits properly. So there also isn't really much of a choice of what coil you can go with either, unless you find something else that will fit... but I would be very hesitant to try something on your own your first time, especially if you aren't familiar with mobile home units.
There is very little to choose from here unfortunately... and if the heater is older, I would highly recommend doing the full system over just the AC when it comes to mobile home systems.