I just bought it, and today I went to put fuel in, the front (normal) fuel neck is factory blocked off. Next week I'm going to get it on a lift and reall be able to check it out.

 

If the front tank is blocked from being filled at the pump, there probably is a "crossover" line that allows fuel from the rear tank to also go to the front tank and maybe only one in tank fuel pump..

 

Hanky, do you mean it could be gravity flow instead of a pump? If so, wouldn't one tank need to be installed higher than the other one? That should be an easy way to tell.

 

Without actually looking at the set up , can only conclude they are probably close to the same level. Depending on which tank has the fuel gauge , the fuel will always be at the same level in both tanks as long as they are at a similar height... We are not able to know all the info with the vehicle being there and we here.

Just about all diesel trucks with 2 tanks pull from one tank , have one gauge, , but the do have a crossover line that allows fuel to flow from one tank to the other. If each tank has a capacity of 100 gals. and the gauge reads one-half. the total capacity is still 100 gals.. Because it takes a long time for the fuel to flow from one tank to the other. that is why you see drivers fuel both tanks , it is just quicker.
The crossover line is usually only 3/8 in ID. The level does equalize, just slowly.