Corzee

I have the stock seats in my 240z, and they are in good condition so i want to keep them for the time being. However I have only the lap belt on the driver side, and nothing on the passenger side. I dont want to deal with a roll/harness bar and standard harnesses. So Ive found these 3pt retractable harnesses by Corbeau that bolt up to the oem seat-belt bolts. ***My question is, will they work correctly with the oem seats, or do you need a seat with a space between seat and headrest, or seats with harness slots, as pictured below. Corbeau belts manggg... EDIT: I found some better pictures to explain. Havent found anyone that has tried these in a Z (and yes ive searched ). any input welcome. Do you HAVE to have seats designed to use harnesses like this: Or can you just use a regular seats with no issues like this: This may seem like a silly question, but im just trying to get a couple more opinions on whether this is safe enough.