Suggest first you check all fuses.
The Courtesy light delay timer also gets a power feed
from the Gages fuse (presumably to power it). The Gages
fuse and downstream witing is live only with the ignition switch turned on according to the wiring diagram. The gages fuse feeds lots of things, including the gauges (funny that!)
So the next thing I would be checking (with a multimeter
or test lamp) is that the gages fuse only has +12V to it when the ignition is on, and with ignition off no longer has +12v to it.
rough diagram for you...
+12V--------->[Ign Switch]------>|---->[gages fuse]---->
|
V
[to distributor]
...so Ign Sw off should remove power to distributor and to gages fuse - and engine stops etc.
Hope this helps !
Chris
______________
Kiwi Chris