So I just bought a Springfield Loaded model.  When I get it I want to convert it from the full length guide rod to the traditional GI style.  What parts will I need to replace?

The guide rod and the bushing plug.

Not the bushing.
Recoil spring guide and spring plug.

Not sure why the links aren't working, but...
https://shopwilsoncombat.com/Recoil-Spring-Guide-Blue/productinfo/R8/
https://shopwilsoncombat.com/Recoil-Spring-Plug-Ringed-Cap-Bullet-Proof-Blue/productinfo/566B/

The ed Brown guide rod and plug from brownells work well with the Springfield.

The Springfield two piece full length guide rod is lame to take apart.
And it unscrews half the time on it's own while you're shooting.
The "free" solution:

1) Permanently screw it together with some red locktite or rockset
2) chuck it up in a lathe and take some length off it until it sits about .005"-.020" shorter than the face of the slide while in battery.
3) Add a little chamfer, maybe .030-050" and polish th ewhole thing well so it functions smoothly.
4) Knock the sharp lip of the hollow spring plug off with some emery cloth on a flat surface and then some scotchbrite.

Now you can assemble/disassemble the gun without tools just as simply as a GI guide rod but still retain all the benefits (imaginary or otherwise) of a regular 1 piece FLGR. My Springfield Loaded, Les Bear 5" Monolith and Les Baer Stinger (little 4.25" officer) all sport full length guide rods.  Personally I love FLGR because I can't stand the sproinginess of an uncaptured spring. And it looks cool. Gotta look cool.

I converted my loaded model to gi style. It unscrewed its self in every stage during a class I took with it. Total pos!
My RIA came with a full length one piece guide rod though and it hasn't been any problem at all. Not that it really does anything better than a GI setup.
I can't believe Springfield is still using that setup.

Yeah I've heard horror stories but it's not why I want to change it.  I just don't like the look of the FLGR, I just prefer the GI style.  My one and only other 1911 is a Loaded Operator model so it came in the GI style.  I just wasn't sure which parts needed replacing on the new Loaded i just bought but I got my answer

My SA TRP came with the 2 piece and I swapped in the Wilson Combat Bulletproof GI rod and plug stainless.  it looks so much better now with the WC plug.

You have to thoroughly degrease the threads (male and female) and then tighten it down well.

Yeah...... Still easier to just use the gi style with no tools and no problem.
These threads come up quite frequently and yet Springfield still uses that system.

People must still be buying them.

I actually just did this with an older loaded model I bought used.  When I pulled the FLGR out and screwed it together on the table top, the two shoulders didn't mate up and it threw the front portion of the guide rod out of alignment about 5 degrees.  (Basically made it look bent).  Made the slide cycle really gritty too.

Anyways, called Springfield and got:
GI guide rod
new recoil spring
plug

For $22 shipped from them.

Ended up adding some spring noise to cycling but the overall function is much smoother without the FLGR pushing awkwardly on the slide.