Fastest and stable method to weld large amount of vertices in 3ds Max?

Default weld vertices is very slow in object with hi-poly count. And welder modifier seems not really speeding up well.

As I know, when attach large amount of poly/mesh people figure out better method than default method used build-in 3ds max. There's many alternative scripts to attach numerous objects very quickly. And quicker than default by very far range.

I tried to search in scriptspot for script that speedup welding process for object contains large amount of vertices (hundred-thousands or higher). Is that script available here under hard-to-search name or it's a totally different story (in term of difficulty to make) compare to poly attaching alternative mentioned above? Thanks.