First off, i'd like to welcome you to the forum, Mikey.
It appeared as if you had the floor right, in the first picture. But in OpenBVE it came out like that. For starters, the front of the train in OpenBVE faces the opposite direction (unless its a double-ended car, I'm not familiar with LACMTA). You've centered it around the axis, that's good. A good idea would be to make the floor a separate model, and then export it. Certain aspects of the R62 exterior were added that way.
BStyles