Here’s a few pics. The one on the right is metal and original. The one on the left is a plastic replacement from a vendor that required cutting to fit. The plastic ones have held up on the rear, but the front ones disintegrated at the bottom I assume from the hub grease. They measure 3 and 1/8 and the original metal ones are a bit shorter. Based on the plastic issue I may look to have the original metal ones replated.
Looking for center caps for my slotted alloy wheels that came with the car when purchased. I’ve seen a lot of talk and ones listed as 240/280z on line, but found these are typically too small. The center cap hole on mine are greater than 3” and seem unique to my 1973 240z.