A standard mainspring housing assembly consists of the mainspring housing itself, a mainspring housing retaining pin which goes in the bottom of the housing and holds it to the frame, the mainspring retaining pin which has a cone-shaped head, the mainspring, the mainspring cap, and a mainspring cap retaining pin.

Does the Springfield ILS system NOT use a mainspring cap retaining pin, i.e. is the mainspring cap allowed to push up against the hammer spur beyond the mainspring housing itself?

Mine didn't come with a pin. The instruction booklet recommends sticking something in the hole to prevent catastophe. The whole ILS MSH is kinda lame and I recommend replacing it with a standard MSH and MSH parts.

Quoted: Mine didn't come with a pin.

Same here.  It never gave me any problems, but I replaced it with an Ed Brown MSH just the same.

You are correct that Springfield does not use the cap retaining pin, even though the MSH is drilled for one.  When you replace the internals with a proper spring and cap, add the cap retaining pin, too.  On the Springers that I have retained the original MSH, that is what I have done, and the results are a standard MSH, with an inoperable lock.

I replaced the MSH and parts on my SA GI Champion.

I found a parkerized GI type Flat housing at a Gunshow for $15 and the guts for $10.

Easy swap - works like it was designed now

Lots of info on  1911.org  forum.m1911.org/showthread.php?t=1595&highlight=replace

Springy gives you a little pin that's shaped like a lazy V to put in the hole when taking it off. There must be some interference with the lock with a standard pin that stays in.

Quoted: Springy gives you a little pin that's shaped like a lazy V to put in the hole when taking it off. There must be some interference with the lock with a standard pin that stays in.

So that's what that thing is for! Mine came with two wrenches, two ILS keys, and that little thingy. I didn't see any mention of it in the manual.

Quoted: You are correct that Springfield does not use the cap retaining pin, even though the MSH is drilled for one.  When you replace the internals with a proper spring and cap, add the cap retaining pin, too.  On the Springers that I have retained the original MSH, that is what I have done, and the results are a standard MSH, with an inoperable lock.

That's the same thing I was planning to do, i.e. retain the original Springfield MSH and simply buy a new mainspring cap and its retaining pin.  I had wondered whether I could use the same mainspring housing instead of buying a new one, and just leave the ILS in place in the unlocked position.  The ILS lock won't bother me in place as long as it stays inoperable.  Thanks!