I would want to ensure that the shell, howsoever constructed, or re-constructed is surveyed and the surveyors report is not qualified through lack of access, blacking making assessment impossible etc. From experience, make it politely clear to the surveyor what you are expecting and do what you can to ensure full acces. Always provide instructions in writing as this helps the surveyor understand exactly what you want done. In addition, if you want a detailed engine check, say so, it's worth it - usually. Happy hunting.