In cab Gas Tank mounting area

[68muscletruck]

Some genius built his behind the seat speaker box a bit to big to fit in his bump with his existing seat mounts. Stock bench seat. I relocated my long in cab tank to the front of the bed and have the free space where it used to be, there is the bulge along the entire back wall of the cab that juts out about 1/4'' to 1/2'' where the three bolts from the tank that is partially in my way, Am i okay to grind this off and still be 'structurally sound', also the two big bolts in the floor on the rise for the brackets that hold the bottom lip of the tank in place, they just spin without getting loose, and looking under the cab its evident that section is like a square tube or something because there is no visible nut on the back since its covered, can I cut the top off of that surface for the box to sit down into since its like a square tubing that goes across the bottom that would still be closed off from the weather and still be 'structurally sound'

[68muscletruck]

basically if i cut those pieces out i can place the box so I just have to slide the seat to the forward lock position on the bolts holes for it, otherwise I need to move it forward and drill new mounting holes, which would probably be the easiest option but I'd still like ideas and opinions on grinding some of that stuff out as too far foward with the seat will be frustrating without a tilt column

[fordman]

ok the 6-69 tank fits into a bracket ont he floor. it is hedl down by the rear cab mount bolts. the botls thread into the rubber washer bushings under the cab. to get the bolts loose you take some vise grips and grab onto the washer/nuts ont he bottom of the rubber and clamp the vise grips onto the washer/nuts. then loosen the botls. the vise grips will spin until they hit the cab support bar. and then stop and let the bolt come out. you can then remove the tank support bracket and put the botls back in. is that what you needed to know?

[68muscletruck]

I figured they were in rubber or something, the nuts on the back of those will be somewhere along the frame rails? guess if that part is one of the cab mounts i'm not grinding out that section

[fordman]

the rear cab mount rubbers are a two piece rubber and metal insert. so for each single rubber it has on metal insert. the cab sits on the top metal insert with the rubber underneath that. that rubber sits on the channel iron the goes across the frame. under that channel is the seconf piece of rubber. it has a metal insert that comes up from the bottom. itnside and made part of that insert is a thread part. the rear cab mount bolt goes down through the whole thing and threads into the bottom metal insert (washer/ nut) if you grind or cut the floor of the cab thier is a support brace right under that point. but you would only open up the cab of the truck to possible air leaks and possible water leaks from splashing mud. maybe. about the only thing you can remove is the gas tank support bracket. the bolt has to go back into hold the cab onto the frame. unless you can figure a way to mount the cab differently to the frame.