Large baking tin - quantity and recipe advice needed please!

[fillybuster]

I'm (hopefully) making a 'Thomas' cake for ds1's 3rd birthday this weekend. I've figured out (I think...) how to assemble the blardy thing but now I need to do the baking....

I've got an 11" by 14" baking tin, about 2.5" deep....anyone got

a) any idea of quantity increases from (say) a recipe for a 10"x 8" tin (maths is soooo not my strong point)

and

b) any good recipes that cut and re-assemble well? I'll need to cut 2 'fenders' off the end to stick to the sides and attach a round front bit (baked bean can baking maybe?) and a funnel as well...

Hoping to do a practise run this afternoon whilst the dcs are busy....! Help really appreciated!!

I have just this minute finished icing a 8" x 13" cake. It wasn't as deep as yours prob about half that. You could use your usual quantities and if too thin, bake another?
The recipe I used was for madeira cake, which was a lot firmer and easier to ice.

250g (8oz) soft marg
250g (8oz) caster sugar
4 eggs
2 tablespoons milk
300g (10oz) self-raising flour
1 teaspoon baking powder
1.5 teaspoon vanilla esscence

Cream marg and sugar together till light and fluffy
In seperate bowl, lightly beat eggs and milk
Mix flour and baking powder together an d gradually beat into creamed mixture alternating with egg and milk mixture
Spoon into linied tin and bake at 160*/325f/gas mark 3 for anywhere between 30mins - 55 mins (mine took 55mins) until cake springs back when pressed lightly

Thank you....my first attempt went horribly wrong so am going to try again later on....!!