Which Ohlins For 19' Street Twin

Whatever you go for check the clearance around the upper mounting lug when you get them before you launch into a full on change out. T100 & Speed Twin owners have had issues with certain brands fouling the mounting lug. Nitron for one, which was my case with a T100. You'll find the threads here easily enough.

Here you go in any case:
https://www.thetriumphforum.com/threads/nitron-shocks-word-of-warning.22186/

https://www.thetriumphforum.com/threads/k-tech-shocks.22225/#post-375445

As for the front, I bought an Ohlins cartridge kit for my T100 and it's a fabulous upgrade. There are other manufacturers producing kits such as Andreani and one or two others. The Ohlins went straight in on mine without any mods, be aware that some makes may not.