@barachius i'm a little bit confused by your post, the ford fiesta has replayable races in chapter 3 so obtaining blueprints to unlock and upgrade the car shouldnt be a problem
completing daily tasks also shouldnt be a problem as there are at least 3 replayable races (inc the boss race) in each chapter that will award parts/cash/blueprints, as you have said that you are up to chapter 5 youve got at least 12 races that are replayable so that you can "farm" for parts and blueprints for the cars you currently have unlocked
alternatively you can sell any unused parts for scrap and buy the blueprints at the chop shop
also the prizes awarded by gold crates are dependant on your rep level (as your level increases then higher rarity parts/blueprints become available), so as long as you collect your free gold crate every 2 days then you should pick up fiesta blueprints from those (at some point)
