Notice the unusual cylinder pipe pairing: 1 with 3 & 2 with 4.

Since diesels are low RPM torque oriented, a good FLOWING system in a naturally aspirated diesel is far more important than having tuned / calculated length header pipes. Equal length pipes impose on the limited space between the starter, steering column, frame, and torsion bar. The underhood room on the exhaust side is already a bit snug. Also, it is not known if the system above is compatible with the presence of an A/C compressor.
So as best I know presently, you could have custom fabricated a compact welded steel tubing manifold with minimal sharp bends ... forget about tuned lengths. This would be quite adequate for a low RPM naturally aspirated diesel.