how much sheet steel ??

[alga]

The cost of steel stock works out at less than 5% of the build cost. Why bother going into detail with that?

If yo do, the only correct answer is "it depends". Do you intend to cut all your 3 mm plate parts, or get some things laser cut? Will you use steel or aluminium for the floor? Will you use a full GRP body kit, or just the nose, bonnet, scuttle, and wings, or will you do an ali bonnet?

But roughly, you will need 3 2500x1250 sheets of alunimium if you're doing the rear tub and the bonnet in aluminium. I'd say you'll need about 1 m^2 of 3 mm plate, about 0.25 m^2 of 5 mm plate if you're doing your own. 10 mm and 1 mm plate steel parts are so few that you can work it out for youself.