All things considered, I would advise against cutting and welding the brake lever.
Make a longer lever from "scratch" or find a longer lever from another bike that will fit and use it.
I replaced the "straight" levers on the '80 R65 with a pair of Kaw. levers,with a "dogleg", from the mid-80s.
[This about 28 years ago tho...sorry, NO pics]