The overall shape is in a good place I think, it has the style and the look of an armoured transport especially the central body, the bulky looking "spine" really makes it look rugged.
Biggest issue, aside from the central body not being attached to the rest of the model of course, is the rear section underneath the engines doesn't match up to the new cargohold area. I'd suggest taking the cargohold and lengthening it so that it reaches halfway through that bar intersecting the engines then gradually merging into the central two engines to give a more solid look.
You may also consider adjusting the rear section between the two central engines to give the impression of a loading ramp, squaring off the bottom a little perhaps?
Alternatively, you could expand that same rear section so that it surrounds the lower part of the central two engines which looks a little bare and having that flare out to connect to the cargohold.
