I recently imported a legacy gtb, just fill in what you can, dont worry about all the boxes, section 11 were it say type approval, just write "Exempt as the vehicle is over 10 years old" also make, model, etc, the obvious stuff that you know. You need to include the mot certificate, Insurance cover note on vin number.The de-reg document both original japanese copy, and an english translation. Also include proof of payment of vat and import duty. Remember to fill in the back of the form as well with all your contact details, and also include a copy of your identity, ie driving license. And lastly a cheque for £55 fee and also 6/12months of tax.