In addition to what folks say above about the engine, it is also noticeably heavier than most of its contemporaries. Greenberg's Guide notes that the power truck is similar (though not identical) to the older Lionel power trucks of the Geeps produced in the 50s. The magnets in the trucks on the 8477 are larger, producing stronger Magnetraction.
If you run Command Control, you'll want the later TMCC version of the engine, as others noted above. But if you have a conventional layout and get this engine, I'd suggest replacing the fuel tank with a diecast one that Lionel put on their later TMCC versions of the Geeps. It is larger than the plastic one on the 8477 and other MPC-era Geeps, and will give the engine a much nicer (and more prototypical) look (as well as more weight). Lionel also later made a dummy B unit for this engine.
Note that the TMCC versions of this particular NYC engine (there were two, cab. nos. 2380 and 2383) have the larger fuel tank, but it is constructed of plastic. The later TMCC versions of the Lionel traditional Geeps have that same tank, but Lionel upgraded it to diecast construction. They are available from Lionel, or other parts sources. (I've done a number of such changeovers.)