I have starting issues with my 68 chevelle. It has a small block 350. I replaced the starter because it was bad, then the car started. I turned it off and it wouldnt start, so I waited awhile and kept trying to start it and finally it did. then the next day it wouldnt start again. I the replaced the anternator because I found out it was bad also, so again once I did that it started right up. I drove it around alittle, came back home, turned it off and it wouldnt start back up again. after several attempts it did. could it be that my ignition switch is bad? I need help

There's a huge difference between "cranks but won't start" and "won't crank".

Which one are you experiencing?

Yup...you need to answer Schurkey's question first, but I'll throw in my 2 cents. When I got mine I chased intermittent starting issues until I replaced the ignition switch above the column. Removed 2 nuts, lowered & supported the column, replaced the switch (2 screws), buttoned it up. Half an hour and no more problems.
Good luck.