91 f250 351w 5 spd. 4x4 replaced clutch. slave cyl. And master cyl. It want go into gear when running. Iv bleed it a bunch of times. when turned of it goes in gear fine.

 

A tip when bleeding the clutch. Remove the rubber cup thing that goes into the reservoir. That way it holds more fluid. One pump, bleed, one pump, bleed, etc.
another thing is reverse bleeding. Pump fluid from the bottom up with a brake bleeder pump thing.

The system is so small that it doesn't take much to goof it up.

 

Sounds like you didn't fill the system before you installed it maybe? Either way it sounds like you still have a ton of air in there. You can try reverse bleeding with a hand held pump or just untamnd said, remove the cap and fill the res all the way and just keep pumping until you get good pedal.

 

I've always had easy success with the bleeder system on these trucks. Pump the pedal a bunch of times if you have to...fast...sometimes you need to pump a bunch to build any pressure if there's air.

You ARE holding the pedal down when cracking the bleeder, right?