i was working on a cobra yesterday and it wouldnt go into reverse?

sure you were putting it in reverse and not 6th?

sometimes if you are having a problem getting it into reverse, try going into 1st, then straight into reverse with no hesitation. If that doesn't work, try rolling the car a bit and it should slide in gear.

i dont know what year yours is but but ford offers a rebuild kit for 5 speeds that updates your shift forks and syncro hubs i know this because i had an issue with mine and i looked up tech bulletins at my shop and that came up. good luck

Exactly what Mike said. Mine does that all the time. Except instead of just putting it in fifth and going back to reverse, go to first and move the car forward just a little. Then go back to reverse and it should be fine.