Fuel consumption/Relief tubes and related

Thanks to all for your good advice. I have now determined that the airplane I'm going to see is a 1973 P337 with Continental TSIO360CB engines. I was trying to determine the range for this specific plane, and it looks like I will be able to make a safe 800nm flight if my rear end can hold out. If I can make a TAS of 190 kts at 16,000' with a fuel flow of 24 gph and a fuel capacity of 123 gallons, I can