lag bolts into shields into concrete may be secure if its done really carefully. it still leaves possible issues with the frame integrity - there are quite a few low quality frames and cabinets out there and mechanical stress on those vertical rails and all of the connection points in-between when equipment is extended on rails is no joke.

I am used to datacentre grade mounting gear (even in my home lab), so I am a bit spoiled. however… take a look at Rack Solutions for harder-to-find quality mounts, rails and adapters. a source for excellent quality steel open racks/frames and enclosures is x-mark (now owned by belden). thats the stuff I use for myself.

edit: as was mentioned in another comment, OEM rails are almost always your best bet, however high quality 4-post sliding shelves have saved my butt on ocassion. Rack Solutions also offers those.