I have had success with MT 1049s. I have used Unimates, as well. The Unimates are usually sufficient, as usually you do not couple up a switcher to them unless you are modelling a big city passenger terminal, in which case you would see that.
If you are modelling Boston and Maine after the late 1970s, when the transmissions failed on most of them and neither B&M nor MBTA would not pay to fix them, you might need to switch them.
In that era, B&M usually ran them push/pull anyhow, with a GP-9 for power. The diesel engines in most of the cars still operated, thus there was heat and air condition, as needed.