1991 GMC K2500 Intermittent Start

[kearly88]

I am having an issue starting my 1991 GMC K2500. Sometimes it fires right up. Other time absolutely nothing happens when i turn the key. If i turn it off and on enough times eventually something will connect and it will start. Other times i have to jump it, and even then sometimes nothing at all when i turn the key. It has a brand new crate 350, and runs great when it starts, but i cant rely on it enough to start to take it anywhere far from home. Any suggestions on what it might be? I have replaced the steering column and had the issue with both the old and new column. Thanks in advance- Ken