having just done the mod with the help of these instruction hoping it cant hurt to add my 2p worth you can learn from my mistakes !
Johns original instructions refer to a Fastin-Faston 8mm right angle connector. Having spent a while searching for the right part I figured out there is actually no such thing which is why everyone had trouble finding them ! They are 7.8mm AMP Fastin Flag Terminals. But there are plenty of them on Ebay, just need to search for "H4 connector" I bought a Durite one which had the correct terminals in brass and the terminals in the correct orientation.
Also, to open up the old connector, you just need to push a flat screwdriver into the central hole between the 3 pins to push the flap open.
If you look at the terminals, you see the small tab which holds the connector in the block. If you want to use your new block you get the old ones out by inserting a thin strong object to push the spring tab back so you can withdraw it from the back.
Here is the power end that plugs straight in to the connector that has a green wire going in one side and no corresponding connection on the other side of the block, that is in the junction box under the fuel tank. It is a 2.8mm crimp terminal. I crimped it, then soldered it for good measure. No need to cut any of your existing connections. The fuse can be removed for MOT's if required. I searched on ebay for "2.8mm terminal latch" - the ones you need have the small locking tab poking out of the bottom to click them in place.
good luck and a big thanks to the original author John Silva.