I'm sure it's been hashed out before, I wouldn't be surprised to find that the Suburban tank on a regular bed truck is too long. That's where the difference is between the 31 and 40 gallon tanks, distance to the axle.
Why run three gauges? If you go electric, no reason not to run one gauge and run each tank until empty, especially with a carb.
With what I was thinking, your sending unit problem is taken care of...all three tanks are always at the same level (if all are filled at the same time) so you only need to run the one sending unit wire. Also, you could fill any one of the three tanks and not have to worry about switching anything. The tanks would either equalize by the siphoning action, or if in the first tank, fuel gauge would drop as "normal" (like a single tank setup) until it reached the level of the other two tanks, when the siphon action would start again. Of course this is theory, but I can't see why it wouldn't work. Two fittings brazed to two sending units, done.
I can see the electrically switched 3 tank setup working fine. But when something goes wrong, you are going to have a hell of a time figuring out what the problem is.
If you feel adventurous, can you report back the difference between a 31 and 40 gallon tank sender? GM uses different part numbers even the same year, and I don't understand why. Depth is known to be the same, fuel lines are on the same side, emissions should be the same for 1/2 tons, so I have never been able to figure out if or why they are not interchangeable. Would open up some options for people trying to get sending units.
Why run three gauges? If you go electric, no reason not to run one gauge and run each tank until empty, especially with a carb.
With what I was thinking, your sending unit problem is taken care of...all three tanks are always at the same level (if all are filled at the same time) so you only need to run the one sending unit wire. Also, you could fill any one of the three tanks and not have to worry about switching anything. The tanks would either equalize by the siphoning action, or if in the first tank, fuel gauge would drop as "normal" (like a single tank setup) until it reached the level of the other two tanks, when the siphon action would start again. Of course this is theory, but I can't see why it wouldn't work. Two fittings brazed to two sending units, done.
I can see the electrically switched 3 tank setup working fine. But when something goes wrong, you are going to have a hell of a time figuring out what the problem is.
If you feel adventurous, can you report back the difference between a 31 and 40 gallon tank sender? GM uses different part numbers even the same year, and I don't understand why. Depth is known to be the same, fuel lines are on the same side, emissions should be the same for 1/2 tons, so I have never been able to figure out if or why they are not interchangeable. Would open up some options for people trying to get sending units.
