exactly, the "kits" being mentioned are put together by parts shops here in USA, (not the shiny clean ones like autozone etc.) but actual engine parts shops which have greasy doors and a machine shop next to them.
When I had my shop in Karachi I had a few select shops in Plaza karachi where I gave them some papers which I jotted down as kits. I would just call them and say I want that "kit" - they would be timing belt sets for engines, complete with rollers, seals, waterpump etc or engine gasket set, or cv joint boots or brake pads including small dust seals etc.. just paid them extra for their legwork to collect the kit.
Made life so simple and easy, get there and you have all stuff packed in one big box for you. Pay up and bye bye. 10 minutes at max. Those parts shop loved that too as they were a tiny shop and had no seats for customers.
