For #8 & 4 I use a 3/4" extension and that's all you need. No swivel etc. SK makes one I think they call it 1/2" but it's more like 3/4.
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i used the delco replacements. Everything went fine, with the exception of i had a tough time getting the new plug to thread into the drivers side front cylinder, i forget which # that is. Thought i had stripped it, but after some patience got it back no issues.
For #8 & 4 I use a 3/4" extension and that's all you need. No swivel etc. SK makes one I think they call it 1/2" but it's more like 3/4.