How to get sponsors for a truck club in So'Cal ?! ?

Sponsors pay money to get their name exposed to people who are likely to buy their product/service.

Think about where the sponsor's name will be exposed to people. Think about the people who will see the name. Will those people be likely to buy the product/service from the sponsor? If yes, what kind of product/service would those people be likely to purchase?

Put yourself in the shoes of a marketing / advertising manager for a company. How many items are you likely to sell to this group of people if you spend $xyz on a sponsorship?

The bottom line is you need to figure out what kind of companies would really benefit from an association with your club. Then contact them by phone or letter and lay out your proposition. The proposition could be something like: "We can expose your company to ### people every week/month/year and these people are your perfect targe market." For $xyz we will put your logo on our __________ (newsletter, trucks, banners at events, etc.)."