This gap here - surely that can't be right?
Nope, the center has debonded I’m afraid. That needs replaced.
Is that difficult to see/check from under the car? Just wondering why I've never notice it till I had the inner plastic splash thing off.
If the condition of the trailing arms themselves are good, not heavily rusty, I’d just replace the beam bushes.
zroadster.org
From doing mine on axel stands and in my own opinion is it’s only a few more bolts to drop the whole thing. You will then have greater access to get the beam bushes out using a press or burning them out if they are firmly in there as mine was. Another plus is greater access for any refurbing of any of the component parts and addressing any rust or lifted undercoating, but if your underside and components are in mint condition it is doable but I think more difficult.