Thanks for the links, Ted.  I only have the square ones but they'd work great on any engine.  

While the HD truck exhaust manifold gasket with the built in heat shield is no longer available except as a NOS item, the shields that came on the cars and pickups are still available.

From the factory, the Y’s did have heat shields attached to the bottom side of the cast iron manifolds for the sole purpose of protecting the spark plug wires.  There were two on each side of the engine and fastened with the same bolts that attach the exhaust manifolds to the engine.  Whether or not they will work with headers will depend upon the header that’s being used.  They are available from some of the restoration houses.  Here’s a link.

Spark Plug Shield for 1954-64 Ford Trucks and Cars | Dennis Carpenter Ford Restorations (dennis-carpenter.com)

Lorena, Texas (South of Waco)

Those spark plug wire holders came as original equipment on all year Ford Y V8’s on both the cars and trucks.  Even the industrial engines had them.  I get my replacements from Mac’s and Carpenters, but they are also available from many of the other Ford and Thunderbird restoration supply houses.

Here are some links.
Eckler's Spark Plug Wire Grommet & Bracket Kit/54-64 8 Cyl Ford Thunderbird Fairlane Galaxie Ranchero Truck Full Size Ford Mercury (macsautoparts.com)

Spark Plug Wire Grommet for 1954-64 Ford Trucks and Cars | Dennis Carpenter Ford Restorations (dennis-carpenter.com) 

Spark Plug Wire Bracket for 1954-64 Ford Trucks and Cars | Dennis Carpenter Ford Restorations (dennis-carpenter.com)

Lorena, Texas (South of Waco)

Ted- those 4 hole plug wire holders that mount on the head, right behind the #4 exhaust port...are those a T-bird item, or where they on Non-T-Birds, too?  I don't recall seeing them on either of my other Y's but my current one has them.  

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Straight boots or 90° spark plug boots?  Here are some pictures of Y’s with 90° boots and headers.
  

  

  

  

  

Lorena, Texas (South of Waco)

Have you considered plug wire heat shielding?

Can you show a photo(s) showing how the wires are running along the headers?

7mm or 8mm?

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Guessing that would be the corvette set that ran thru the shields that went under the manifolds. Similar to the y block. Been a long time since I ran a set of those.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Larry's Thunderbird's sells a stock replacement set of wires, and a performance set.  I have heard that there is a SBC set of wires that fits a 327/350 that runs the wires under the exhaust manifolds that will work just perfect on the Y.  Any SBC universal set with proper boot angles should work.  Joe-JDC

JDC

I’m running a set of reproduction wires on both the bird and the roadster, never had a problem with the FPA’s on the bird or even tighter headers on the roadster. Both with MSD or high output ignitions, and I saw the FPA’s starting to flow red on the chassis dyno. Stock mounting brackets.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ