Angus242164;32999 wrote21mm front and rear was standard on GLE's from '81 onwards, and then standard on all trim levels from '85 onwards, so they're pretty easy to find. Wagons may have retained the 19mm bar on the rear after '85, not sure.
23mm is hard to find, only used on some 242GT's, '79 only rings a bell.
IPD sell excellent quality 25mm bars, be prepared to spend some money though as they need to be shipped from the US.
Some people have used Falcon front swaybars with success, though I haven't done it myself so I can't comment.
With your proposed spring/shock combo, I'd just get a set of 21mm bars from a wreckers (or maybe somebody here has some) and see how you like it. If you find it lacking later on, then you can save up for some IPD bars.
I measured the rear one on my wagon and it was 17mm, I could have measured wrong though as I did it quickly. Yeah I called up a few wreckers and they couldn't find any.
I was looking at the IPD ones but when shipping is so expensive it will be something I do last I think.
I want to try the falcon one out and see how that goes but I just need to know what falcon to get it from.
Thank you for your input!