Not knowing 40 chevys at all... I welded up a simple set up, a couple pieces of flat stock (& padlocked together) to my under hood latch so the lever could not move to open the hood.

When I re-wiring the 51 3100, I also added a 1-form C relay to a common switch. The directions said to use the heater fan switch but I added a two stage safety/fog lamp switch to the dash. You now have to pull the switch out to the first ''safety'' position to start the truck (2nd pos. is fog lamps) otherwise the voltage from the tampered hot-wired key switch would go to the HORN and blow my FIAMMS @ 130dB.
Send me your fax # and I'll send you a copy of the wiring diagram.
It's easy.

Jim & Caroline
The highway is for gamblers, better use your good sense."
Gooday-that's my 1¢ answer due to the lousy economy ~ cause I ain't got - no . mo . doe
Every Shaver | Now Can Snore | Six More Minutes | Than Before ... | Half A Pound for Half a Dollar | Spread On Thin | Above the Collar || BURMA-SHAVE