Don't block Eivl, he's the one that told you the right thing. You don't need any of the three items you linked to in the first post. The first is a conversion kit for a cassette freehub, you have a thread on freewheel. You need a single speed bmx freewheel, and you'll also likely need to redish the wheel. The second link is to a tensioner, you don't need that on an old road bike, as it will have horizontal dropouts and you can set the tension just fine with those. The third link is to a 1/8" chain, you don't need that, you need a regular old $8 3/32" road chain.
Nitro is right, you need shorter chainring bolts, or at least some washers. You'll also need a chain tool, a freewheel remover that fits the old freewheel, and a spoke wrench to redish the wheel. Any LBS will have all of this stuff, no need to order online.