After much research and input from others who have tried modifying a non-Suzuki Savage tank two things are apparent...first after the purchase of a new or used tank you MUST modify existing mounts or make new ones, second (and MOST important) the tank needs a wide tunnel to clear the decompression solenoid mounted on the frame. I found this modification to be my best option and had it done.....
Take your OEM tank to a sheet metal fabrication shop and have them cut BOTH sides off and weld in 2" of new sheet metal to each side to widen the tank.
NO fitment issues and this mod makes the tank holds about 4 gallons.
Sand & bondo the welded seams, (assuming the fab shop ground the welds smooth for you), repaint and VIOLA, a new, larger
tank for much less than purchasing and modifying an aftermarket tank.
Make sure you drain ALL the gas out of it and flush it out with LOTS of water and remove the petcock & speedo before taking it to the fabrication shop!