Speed runs of Final Lap Twin are already done with use of having multiple fuel tanks in your inventory. Fuel tanks are very useful and are the cheapest item you can buy. The current strategy only uses two. But what if you could have five? Six even?

Having as many fuel tanks as possible will eliminate the need for Bodies completely and make the run much faster and safer. Of course, the five most recent fuel tanks are more than you will need, especially later in the game, but using each of them will cut several seconds off of each encounter. Just remember that swap them out.

One more thing: visiting the fuel refill place fully refills all of them, not just the fully equipped ones. You only need to buy a few motors and tires here and there if you take full advantage of this.

bodies are more important because they allow you to completely skip encounters.

Wrong. Bodies cost money, they don't allow you to skip many encounters (approximately half of the encounters in the first half of a trek from town to town) and less encounters means less money.

Another strategy: Getting the best motor and simply tapping the accelerate button to turn better.