Originally Posted by vw7674
Given the length of those bolts, I would expect a couple of tensioning springs & washers would belong on the bolt-head side.
Usually see that arrangement near a down pipe to a catalytic converter.
No, just the only pair of matching hardware I could find in my box of used nuts and bolts of the correct diameter. Between the two flanges and a gasket, there won't be all that much threads exposed after tightening the nuts.