if you get a solid aluminum or nylon button, you can grind it down till it fits under the cover. providing you use small headed cam bolts. diamond make a real nice rollerized button, but you gotta dimple the cover. shoot for .006-.012 on end play
for a chain, either use a rollmaster or the 440 source gold chain
here's the rollerized one on my hemi, that one requires some work on a stock cover. probably easier to go the other route.