over rotating the key to crank ?!?
 

I was having problems in my 73, as it required muscle power to over-rotate the key to get it cranking.

I replaced the key cylinder; but it is the same turn with brute force past start and hope it cranks.

Has anyone had this happen?

Haven't personally, but a friend did. It was the switch, not the key assembly. I think the switch was at the lower column, (near the floor) if I remember right.

Makes sense what val said. Its an easy cheap fix too.

You replaced the key cylinder, but the ignition switch adjustment is actually your issue. Yes, the switch is screwed to the top of the steering column, about halfway between the dash and firewall. When you turn the key forward to start, the lock mechanism pushes a metal rod forward (down the column) to operate the switch, and it appears the switch isn't being moved far enough. The switch has slotted mounting holes so that it can be adjusted. You need to slide it up a little, more towards the steering wheel, so that it hits the start position sooner. Don't go too far, and re-check the other key positions to make sure they still work in the correct spot.

LOL I had the one in my 78 stick in the on position. As soon as I hooked up the battery, vroom!!!

Ooooops!!! Hate when that happens. ;)

Learned a lot that summer.