Managed to get the chassis painted and weathered. The engine is now in its final resting place. I just mocked the cab up to make sure everything clears. I had to move the hood hinges a little, but it should all fit. It sure is tight though!
I buy most of my styrene online. It helps to have a bunch of different shapes and sizes of styrene round stock, round stock, and angle. Since I do so much scratchbuilding I keep most sizes of the common shapes on hand. Then I just buy some .040, .060", and .080" thick sheets for larger components.