Some nice work there
Most gear levers sit approx 6cm behind TT5, tho this is usually dictated by the reverse light switch on the type 9 box, but as you are not using that box I,m not sure of the position of your gear lever.
My own engine sump is 25mm below the bottom of the chassis, & if i remember correctly ( car not at home) there is 17cm above the top chassis rail to the underside of the bonnet where it meets the scuttle, tho I,ll double check that measurement for you tomorrow.
cheers
andy