Slant Six - exhaust manifold hardware?

Badvert65 said

Referring to the attached photo, the pair on the right is directly off of a slant six in a 1983 Dodge truck. The washer has a straight center while the nut has an extra tapered edge to fit into the washer.
The one on the left is aftermarket, the nut is straight (no taper) and the washer has a bevel in the center for the nut.
I am just wondering if the aftermarket one will work as well as the OE setup because a new factory style nut is impossible to locate.
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I don't think the aftermarket one will work nearly as well. The tapered part of the OE nut has a good amount of meat there to grip inside the washer. The aftermarket nut will basically just grip on the 90* edge of the slotted part of the nut with what looks to be like 1/15th of the surface area.

No idea if it'll work or not work but I don't think it'll work as well.

Then again I've been using a regular nut and washer for 20 years and it hasn't failed me yet. Most important thing is to not over torque.