[Daves55Sedan]

If it has a Y-block engine, the last place I would run the cables would be between bottom of intake manifold and valley pan.
These engines all have a series of rubber grommets and brackets that hold the cable sets to the engine block and away from major heat sources.
When a Y-block engine is in the car, it is not a simple job to replace spark plug cables.
A couple moths ago, I put new cables in mine. I bought a duplicate of original set from Ecklers. They had the spark plug numbers embossed in black on a white piece of plastic near the spark plug boot.
Plug all your cables in at the spark plugs and run the cable sets under the exhaust manifolds. Test fit both your rear side brackets first and mark the plug wires with a piece of chalk at the edge of the bracket. Then take the cables back out and install your side grommets and brackets on both sets and re-install them. Now do same thing with the two rear brackets and grommets. Once the brackets are bolted down, you can now plug the cables into the distributor. It took me a couple nights to do the complete swap, so probably 8 or 10 hours, but I'm kindof a perfectionist and wanted to get the cables just right so there was not to much slack on the sides, but there was still plenty of length to plug in the spark plug boots.