I'm not sure if many of you guys have already done this, I did this on my last celica and I just did it on my new one today since it's easier to find red side markers than the stock yellow ones. And the red ones are the same ones found on the Camrys, Corollas, and back of the Celica coupes. So I thought if anyone wanted to know I'd just write this up, even if no one here is really interested someone outside of the forums might search for it. So here is my min tutorial to doing the swap properly.
The stock one

if you use the same side marker as the ones found on the rear fenders of the Celica coupes you have to use a different hook up. Since the stock front ones wont allow clearance for the red side markers (I think there might be one that is found on pre 83 toyotas, but haven't checked)
Stock side marker light bulb housing.

So I cut up a couple bulb housings that would fit the new side makers (might be able to transfer the smae housing found on the rear celica coupe side markers, but I didn't really have access to many coupes) These came from mainly Camrys. I I attatched the celicas cable to the new ones I pulled so it would be more convienent if I needed to chang ethings.
Modified adaptor

After that it should be a pretty quick plug'n play. Even though the side marker says TOP at the top of the side marker you have to flip it upside down to make it fit in the hole. So if it seems like it doesn't fit just flip it and see if that works.
Red Side marker

And then screw it back on :D

the red side marker is a little larger than the stock yellow one, but I like the way red looks better