Schumacher lists both styles for their poly spool mounts; part number 73PA for the 273/318 engine sizes and 73PLA for the 340/360 engine size. Looks like they are currently out of stock.
I don't have factory part numbers, but I see what you mean on part stores only listing one style, and it's unclear which style that is.
If you don't want to run a spacer (does not need to be welded) and you can't find proper listings, you need to find used factory mounts and just replace the insulator inserts that are available separately.
I am running the Schumacher mounts on mine.
