perhaps a fire truck
Before we get started I'd like to point out that a Professional Engineer's standard of care typically includes a site visit to assess field conditions and get an overall understanding of the structure. This can obviously not be accomplished through the internet. The information provided here is meant for informational purposes only (general sizing and budgeting) and is based on the information provided by you. The information should be verified by a professional engineer who can visit the site to ensure that potentially important information has not been overlooked or omitted.
With the firetruck loading, you want W18x106 beams AST A992 Gr. 50. You might need a heavier deck, too. I assumed a 6" deck for loading purposes.