Project idea...

[InkedMuttley]

Only problem I could see is that what weight you've lost with chopping the roof off you're gunna get a fair bit back using the metal to reinforce the structure which you will need as otherwise it'll just be like driving a giant metal jelly although you could do a sort of structure that welds in to each corner sort of like a cross shape and then brace it through the middle stick some dynamat or something between the cross sections to keep the noise down a bit and add a bit more bulk and then false floor it...could be viable and fun!