I have a '96 2500 with the 7.4L engine. When cold, it cranks ~10 seconds before it fires, then it stubles and smooths out. It starts hot fine, but if it sits for 30 mintes or longer, it is hard to start. I also have a misfire code.

I put a fuel pressure gage on the car today and it has 50 psi during idle, bumps to 56 psi when I turn the key off. The gage has been on the car for 5 hours now and it has not leaked down one bit.

What should I look for now?

Next time it's cold, cycle the key on and off several times without starting it, leave it in the run position each time for 5-10sec. If it fires right up after that, your fuel pump is bleeding down pressure and will need to be replaced.
I can't remember the exact pressure, but there are multiple references on the forum for the required fuel pressure; I think it's min 56psi at idle.

Fuel pressure is low.
specs 56/63 lbs
You should be seeing 60 lbs. cold start on cranking and 60 or more running.
Low pressure will not squirt injectors on a cold start.

Tried it today at lunch. 40 degrees outside and cycled the ignition 5 times, allowing the pump to run for 5 second each time. No change, it did not start right up as I had hoped.

For a cold start.
You need to get the fuel pressure up to specs.
You can not leave home without it.