[ZOERA-SC7XX]

Unless someone knows something I don't, you're just gonna have to drop the rear. That's the only downside on the ERA cars with Jag rear ends. Even the big jags need to have the rear dropped to do a brake job. Maybe hire a qualified mechanic to do the job.
Your car is quite old. Call ERA and talk to Doug. Some of the older cars have the XKE subframe. Doug will tell you straight. Good luck.