The original LLV was designed as a custom body atop the Chevrolet S-10, including using the original drivetrain. Everything aside from the body comes from the S

The original LLV was designed as a custom body atop the Chevrolet S-10, including using the original drivetrain. Everything aside from the body comes from the S-10, hence why they were able to keep them on the road for so long. Even as simple as it was, the LLV was a major departure from the Jeep DJ-S, which was just a modified right hand drive Jeep CJ-5 with a sliding side door. In both cases the off the shelf parts available directly from the manufacturers extended the service of first two official USPS mail trucks well beyond their intended lives. Something which is unlikely with Oshkosh given the heavily custom nature of it. Refits to the LLV have included buying drop-in replacement LED headlights to replace the original square sealed beams since the form factor is a standardized part shared across the entire automotive industry from the 1970s onwards. Meanwhile the headlight assemblies for the NGDV are custom made, from the shrouds to the LED driver boards (an expensive problem shared with most headlights these days). We may have a similar problem to the Cadillac XLR's taillights where the driver boards make it infeasible to replace them.