Or...if you have a TR2 or TR3 gearbox, you could simply purchase a transmission cover with the hole already drilled in it, and transfer over any shifter mechanism parts you need to in order to maintain a smooth-working mechanism. Having the dipstick hole in the top of the cover makes refilling the gearbox very easy when changing the lubricant. Using a small funnel and one of today's squeeze-bottle oil containers, it's much easier than using the later-style side plug for filling.