That should fit. For some reason some fit to loose and you might have to make a thin shim to go behind the sealing washer. Then again you might be good.
The Spectra I bought is actually pretty tight. I use it as a breather and oil fill.
Thread revival - I just bought the Spectra one also and it is a very tight fit with the oil fill hole in my cast aluminum Mopar valve covers. I thought you meant it seals tight, but it is actually difficult to insert into the hole before twisting tight. At first I thought it didn't fit at all. It took a few tries making sure it was inserted square and with some down force and it locked in place. It's a lot tighter insertion fit that the flat mopar twist cap that I had on before this.
The diameter was ok on mine. If I recall correctly it came with two rubber seals for the vc sealing surface. I used only one. it was snug to turn but works well.
