Has anyone ever considered or added a pickup side of frame fuel tank into a Suburban? I would like some additional capacity and have long thought of adding this type of tank. The problems I am facing is how to fill the tank without some serious cutting. If I use the current fill point how to add additive to the forward tank.

In the past I have added additional tanks to older station wagons by putting them in the rear seat foot well, crossing the bottoms of both tanks and venting the top back to the fill point. The side mounted tank is just too far apart to consider this type of transfer. I have answered the fuel pump question using an external Carter pump and just tranfering fuel from the new tank to the original while driving using a seperate fuel guage on the new tank.

Any thoughts?

Don't know for sure but I've heard there are clearence issues with the floor being lower in the Sub's.

The floor clearance would be the first problem - the pickup frame kick-up begins just under the cab, remains high back to the bumper, where the Sub kick-up is over the rear axle.

The fuel tank designed is stepped to fit beneath the lower p.u. cab area and the higher bed area, so you'd need to get some good measurements for comparison.

Boneyards are good places for that, since they mostly immediately remove the fuel tanks for saftey - check the Sub vs the XC vs the CC frames, maybe even the standard cab in both frame options.

You might compare an Astro van tank for that area.

The transfer-pump scheme is used in some oem dual-tank setups, but usually have a filler-neck on each tank.

Don't be skittish about crossing marques for some different choices - Ford or Dodge setups may be just the ticket.

The Astro van tank filler is side entrance, where you could run an extension, attached in the left rear wheel-well, fillable from there - most of the filler tubes are connected with a stiff rubber hose and clamps.

Wouldn't stop me to cut the fuel filler-door area from a donor vehicle, have it blended into the side of mine, for the extra convenience of dual tanks.