I know this is not gt related but I figured some of you guys may be able to pick up a few tips on here, I had to replace the tank on my stationary engine. started by mapping the entire tank out on paper so I knew where things go when I need to reassemble , traced out the tank shape and cut the top and bottom sections out . once I was positive I had all good template and dimensions I cut the old tank apart, I needed the fitting for the new tank.
be careful cutting into an old tank you never know what you will find, I found two baffles and the fuel fitting had a flange on the back . removed all the old fittings and brackets to re-use them on the new tank. tack welded the fuel inlet fittings into the inside of the tank , then made the baffles and welded them to the top cover. I drilled 1/4" holed in the tank where the baffles will go so I can spot weld them in place, easier and looks cleaner . put the side of the tank on starting on the flat section and wrapping it around the tank to assure the correct shape , tack as you go every 2" or so. put the top section on the tank using the same procedure.
once that was done I started to weld it together, start between the tacks and weld toward a tack, keep going in the same direction all the way around using 1/2" long welds, keep moving and don't put to much weld on to keep the warpage down .