340 exhaust manifolds???

Not sure why those special extended nuts were needed. I don't doubt the factory used them, but I didn't find them neccessary.

Here's a photo of the passenger side. Looks like I used 2 washers on two of the bolts as well as the super heavy dished washers on the studs.

Lemme look at photos in some '68-'70 magazines to see if they show this detail.
edit: nothing in my stash has a good photo of this from '68-9