The LA243 arm was from the "mid-rear conversion" not the stock ZX5. The original LA220 ZX5 rear arm is the longest of all (2mm more than a ZX5-SP/FS / RB5 rear arm).
The original RB5 / ZX5-SP/FS rear arm is the shortest, part # UM503 with RB5 front arm and LA255 as Nick said with ZX5-SP/FS front arm.
Add in about 2 million driveshaft and shock shaft combinations, stir and serve up a perfect helping of confusion
PS:- get rid of those 3 hole hubs, they split along the hole lines (or perferations as I call them) like tearing sheets out of a cheque book ... which you will need if you keep running them
