I couldn't find anything in the factory shop manual about how the manifolds go together. There is a 3/8 stud on the exhaust manifold, and a pair of 5/16 3.5" hex bolts that slide through the intake, thread into the exhaust, and then there's a nut on the end. I don't recall seeing washers on any of these. Should there be?

Also, does anyone have a source for replacement through bolts with the right length of threaded and unthreaded shaft? Do you just use fully threaded bolts? My originals are probably OK to reuse but I was going to replace them if I can find the right ones.

on the last set of slant manifolds I had apart, I went to McMaster Carr and got (I think they were) 5/16X4" #316 stainless bolts and used those...jury is still out on whether that was a good choice.... I haven't had it on the road yet, only a couple hours' run time in the driveway/garage so far.....
I bought 2 lengths, just to be sure so I only had to pay shipping once.... I don't remember if the 2nd set I bought was 3-1/2 or 4-1/2 length.... Id have to go look, garage all locked up for today.... 5:30 AM will be here way too fast for me to go look now, haha...… I can go look and report back tomorrow if you want.

I have the same thing in my book. 5/16-18 bolts, but I don't list the lengths.

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-MattMan
LEANED & MEAN

I would use regular grade 8 bolts and lots and lots of anti-seize paste on the threads. Last time I bought a set of bolts they came from a big box hardware store.

Even better, if you have broken bolts in the exhaust manifold and have to drill them out anyway, just drill out the threads and use washers on the bolts to clamp the manifolds together. No threads in the manifold means no bolt seizing to the manifold.

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Casually looking for a Clifford hyperpak intake for cheap.

What Reed said has worked for me. And lots of anti-sleaze. If you choose to drill out the threads, use the long bolts, washers, and plain nuts with split-type lock-washers. Mind the recommended torques, as over-torquing any exhaust component causes stuff to crack or snap off due to the heat expansion.

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

I just did this last night. I used all thread and cut it to length. The bolts I found didn't have threads up high enough so I basically made my own.

Good idea. Keep an eye on the all-thread, as it is usually a softer steel than grade-8 bolts, so may fail with exhaust heat.

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)