Depends where you want to install it? I've got a Tripmaster in the Stratos replica, it uses an 8:1 T piece that fits directly onto the back of the speedometer with the drive cable plugged into the back to the T. This is an example but I'm not saying buy this one!
https://www.ebay.co.uk/itm/Halda-T-piece/264762753941?hash=item3da5170395:g:uMkAAOSwaKZe5P7SThe seller seems to have a few so if you can identify the thread size/pitch on the back of your speedometer and he can match it then it's plug and play with a couple of caveats! The cable may rotate in the wrong direction in which case you dismantle the T piece and put the output drive into the other side of the casing. Secondly, you'll need to calibrate the Twinmaster with the right set of drive wheels.
Alternatively, you can send your existing speedometer cable to Speedy Cables with Halo T piece and an instruction where you want to fit the T piece and they'l make you up a long and short cable with the T piece in the middle.
The works Stratos also used Tripmasters/Twinmasters but in these installations the drive was taken from the front wheel with a threaded boss on the back of the stub axle which was drilled through it's length so that the cable drive appeared on the outer end and was driven using a square hole in the grease cap!
Guy
