By "fasteners" I assume you are talking about the 10 triangular "butterfly" washers, the 2 brass plano-concave washers, the one steel cone washer, and the two acorn nuts. They are indeed getting hard to find new. There used to be a package containing all the necessary washers and a pair of acorn nuts, p/n 3744 826, but it's NS1 (no longer available). The triangular washers show as still available individually under p/n 3751 636, the plano-concave washers under p/n 3751 637, and the central cone washer p/n 2121 223 has been superseded to 5301 0091. The acorn nuts are NS1.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

i have some of them ive got ones for my engine n some extra ones howmany do i need for my engine i can sell you them but i hafta count make sure i have the right amount for my engine..

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87 d150 2bbl carb 225
79 f250 300 v8
97 cavalier z24
83 f150 straight 6
89 f450 diseal 4x4 dually 5sp

If the term fasteners was meant by you to include the nuts, I like to use, and Slant Six Dan has mentioned before, Dorman brass nuts. Easy to get, look nice, don't bond to studs. I always use anti sieze like C5A or other copper containing material. Once you get the slant habit, you will live to remove the manifolds every now and then to try something new out.

Dan, I love that term "plano concave"...about says it all!
rock
'64d100

The brass washers are ordinary hexagon washers, for use on all studs except the top front and rear, which originally got — excuse my previous incorrect terminology — castellated nuts, not acorn nuts. You can still get castellated nuts, see for example here
.

It appears the industry calls "acorn nut" a nut with a fully-capped end, such as these:


The slant-6 top front/rear stud nuts aren't quite exactly like the castellated nut shown at the link above, but they're close. I suppose if one really wanted to get super-picky about it, one could buy some brass acorn nuts, grind down the domed cap so as to expose the threads, slot across the diameters three times, and bevel the edges...but I think I'd probably just go ahead and use a standard castellated nut unless someone comes up with a source for the 100% original genuine "half acorn castellated" type.

Over the years, there've been a variety of washer arrangements. The final arrangement was ten triangular butterfly washers, one conical steel washer (top centre) and two brass plano-convex washers (top front & top rear). But earlier setups used three of the conical steel washers (top centre, and on either side of the central intake runners #3 & #4), two of the brass plano-convex washers (top front & top rear) and seven(!) of the triangular butterfly washers. I tend to use the later arrangement (10x triangular butterfly and 1x conical steel washer, all held on w/brass nuts, plus 2x plano-convex washer held on w/castellated nuts installed right way round).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

the top intake part of a manifold on all the engines ive taken the manifolds off of all had triangle washers. and the exaust part had wierd circle shaped cast washers i donno if that helps but i have i bet 2 extra sets of them lieing around
Dave

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87 d150 2bbl carb 225
79 f250 300 v8
97 cavalier z24
83 f150 straight 6
89 f450 diseal 4x4 dually 5sp

Mine didn't have any castelated nuts, although they probably were just long gone. Any idea why they used these? Usually castelated nuts are used with cotter pins.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

The Castilated end was installed toward the recess in the brass washer. As the nut was tightened, the recess in the washer squeezed the splits on the nut down on the stud, so you could curse the stupid engineers, when the stud snapped off, while trying to remove the manifolds.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

My understanding is the castellated nut was used with the castles nestled in the conical side of the washer so as to provide a little bit of controlled "give", so the manifold could move slightly with heat expansion. When everything's installed the right way round, it works well. Evidence? Well, sure: This one aspect of the slant-6 manifold mounting system remained identical from the first 1960 to the last 1987 engine, despite lots of other changes.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

What I do about the manifold nuts on the extreme front/rear studs is every time I visit the junkyard, I get what I can. It's very iffy; sometimes you get a perfect one, sometimes it comes with the broken off part of the stud, and sometimes you get the whole stud along with it. Small items like this are usually free especially if you buy other things at the same time. As a long-term activity, being just one of those slant-six thing you do, you always have what you need in your miscellaneous parts box. And of course, always use antisieze chemical on the threads even if the factory didn't.

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1964 Dart 225 1966 Valiant 225
1966 Dart 273 1966 Barracuda 273
1969 Dart 225
'64-170 engine '66-170 engine
(two) 198 crank/rod sets in custom-fitted wooden boxes

wooden motor scooter with hybrid-electric drive