This article basically is - "The USPS trucks look that way because USPS design says they have to". It would have helped to explain why USPS has these specific requirements - safety, comfort and efficiency.
[1] https://beta.sam.gov/opp/588f5ed4becd4fc4abf6df8e7a918184/vi...
Edit: This[2] seems to be a notice of the contract being awarded to Oshkosh for exactly $481,877,752.00 USD.
[2] https://beta.sam.gov/opp/1e56c386808444d886124fc1927f4eb0/vi...