There was some teenager out there messin' with this car, ya know, and it musta been him that cross-threaded the ICM screws...

The screws attaching the ICM to the heat sink are pretty darn soft, so I'm assuming they are part of the heat transfer? The hardware store guy doesn't know anything about it. What kind of metal are these screws made of, and what'll happen if I put regular steel ones in there? Or I guess some dissimilar-metal-corrosion could happen...

Is there any reason I shouldn't drill these screw pieces out with a slightly bigger bit, and just put bigger screws in it? I don't want to wait for a new heat sink to get here. This is my only running car at the moment. Or I hope I will have a running car soon.

Are you talking about the power stage / Ignition amplifier mounted near the battery?
If so I think any old screw is fine, but get some thermal heat sink paste to install it.
Dan

Yep, that's the one. When I make ASSumptions, it often turns out that something that seemed to make sense, caused a major problem...

I'll bet no mistakes were made with regard to cross threading. The screws are ordinary (steel), but the heat sink is aluminum. One of the reasons I don't routinely advise folks to "replace the heat sink compound" as one might do in their personal computer is these screws are corroded into the casting and may twist right off when removed.

Any means of clamping the module to the heat sink will be effective. The problem is the ignition amplifier is in a bad spot for corrosion, with the battery in back of it.
--
Art Benstein near Baltimore

“The single biggest problem in communication is the illusion that it has taken place.” George Bernard Shaw