That speedo is really good, I had a 60A, it's reliable and it should be more than enough on 10.5T motor and you can add more boost to it. I ran mine with 6.5T and it get little warm with fan on
but if you really want 120A.... you can get 120A called Tyrannosaurus 120A on ebay for £40 but its a knock off copy and It works with hobbywing ESC program card/software.
http://www.ebay.co.uk/itm/Tyrannosau...item51b8a7badc