I did mine separately (disassembled the entire front clip), and it worked out well, but wish I'd done it all in one big chunk; doghouse and cab together because once I had the cab on the frame, and started piecing together, stuff just didn't line up like it did. Took me HOURS of frustration and Budweiser
to get the lines looking good again.
Have some friends hold the front clip, and do it all at once.