Hi guys, just found this forum and thought I would post. I know this is a bit old but here goes.
The spring perch doesn't "really" need to be removed but it is a bigger diameter than the corolla ones. The corolla top spring mount and spring will go onto the RA40 strut but the spring wont sit properly in the bottom spring perch. This is why I will be swapping the celica spring perch for the corolla ones (unless I come into some more money and splurge on adjustable coil overs ). I haven't done this yet as I am still slowly doing the engine swap and will concentrate on the struts after the engine swap and body work is done.
The ride height will only be too high if you try to use the celica springs (which wont fit in the strut tower anyway).
As for the corona strut upgrade, if you are doing the full corona, hilux, peugot upgrade then it will be A LOT better than the RA40 upgrade. The reason I am using the RA40 struts is because I got them for free. The RA40 discs are solid but are still a fair bit bigger than the standard corolla ones. I have pics comparing the two on my web page (click on the link in my sig :| ).
For the master cylinder, I am going to use an AE71 master cylinder and booster. The master cylinder is the same bore as the RA40 and the booster is bigger than the KE30 one. :P .
Hope this is helpfull to others thinking of this upgrade.