The MBTs total Sensor rating is thus 5. For example, the Family Car has 20cf of cargo space. That is, pounds x .454. Its Load in SR is 636. This should be a fairly simple matter to convert.
Dwarves treat seating as one level better.
Also remember to note that crew stations are listed apart from passenger seating. This is up to the designer and game master. For example, the Family Car obviously has two front seats and a bench in the back. This should list the fuel used by the vehicle and how much it has. Multiply gallons of fuel by 3.7 to get the amount in liters.