The only cars with an EXH light in the dash were 8V. To reset the lightm there
is a push button under the dash just to the left and below the steering
column. You can trace the second speedo cable from the instrument cluster to
it by removing the left speaker grill.
The 8 V have a single wire sensor, mounted in the exhaust before the catalytic
converter. Like most sensors, it is 22mm(7/8).
Ywan Mason