If your sliders are the "two studs one above the other and a Y bracket to the mudguard" like mine, they appear to have threaded buttons brazed to the leg, carrying the studs. In my case some fool has replace the stud (brazed in place) so the inner end is proud of the slider bore, and will catch the bottom stanchion bush on assembly. Good chance the stud can be drilled out, thread cleaned up and a new stud fitted Loctited in place. Impossible to tell if the good studs locate in the slider tube itself, and in production these proud ends would be machined off prior to a final finish to the bore. Needless to say whoever played with this one was heavy handed.
As mentioned, welding carries the risk of distortion, and without checking, mine may already be not far from scrap.
With regard to Helicoil repairs, the Helicoil Tap in the kit cuts a thread such that when the coiled wire insert is installed, the inner thread ends up ready to accept the chosen bolt or stud. The tap is the secret, along with consistent size and wire profile for the inserts.
Swarfy.
