Probably your ignition switch located on top of the steering column underneath the dash. It is very inexpensive and easy to replace. Remove the two bolts under the dash that hold the column up and you will be able to lower the column enough to access the switch. Think I paid like $15 for a new one on my '76. - Mr Diesel
'76 C30 Crew 6.2
Thanks for the info eveybody. Looks like I'll be pulling it this week end. 1979 Silverado C10 w/ Olds 5.7 Diesel
85 C10 Custom Deluxe