My bad, here is a picture.

After another thorough cleaning, getting that blocked passage clear making sure everything else was good I made a gasket for the carb. Had a gasket for the exhaust side and already had a new one for the air cleaner side. Put it all back on and it started easier but still wouldn't stay running. Pulled the air cleaner and started it up and was able to keep it running by using my hand over the top to control air flow. I'm not sure what could be causing an air flow issue with all new gaskets. It's nice I can keep the pony running but I can't turn the diesel over while needing one hand on top of the carb feathering air in. If any of you have run into this problem before I'd be interested to hear how you fixed it.

Think I'll just have to buy a rebuild kit, none of the jets are clogged but wouldn't be surprised if they had been cleaned with wire previously and enlarged. Unless someone has a better idea that's my next step. In the meantime I can get it off the trailer when the guy comes back to pick it up with a second set of hands.

Your hand is acting like a CHOKE - Causing the mixture to be rich enough to support combustion. Still the starting engine will not run above low rpm, simply because it is not getting enough fuel! The supply is compromised between the fuel tank and the intake valves.

That open hole into the intake as shown in your picture -
Memory says there was a "filter" in there that allowed fuel to escape if the float stuck and fuel flowed freely.
WHAT HAPPENS IF YOU PLUG IT OFF WHEN THE ENGINE IS RUNNIG? DONT USE YOUR BARE FINGERS!

For kicks and giggles - cut yourself a small wooden plug like a tree limb and plug that hole, see if that does not allow the cylinders to pull the mixture through the carburetor.

Everything you have been saying all along is TOO LEAN, NOT ENOUGH FUEL!

Any air from outside source between the caburetor and the cylinders on the intake side will cause LEAN MIXTURE

Back to basics!

Stick wouldn't seal it well enough but a bolt in there that seemed to seal a little bit better but still needed hand to keep it running. Tried to use a pick tool to plug the tiny hole inside the bigger one and couldn't get it started again. Not sure where it could be pulling air from aside from that.

I attached a pic of the parts catalog that shows what should be in that hole but of course they are discontinued items through cat.

A green limb whittled to a cone seals better than a bolt in most cases because it will flex to meet the imperfections. A bolt is straight thread and does not seal well! If you have good seal between the carburetor and the intake manifold, that missing piece would allow air to flow in, reducing the flow through the carburetor. Ensure your carb/manifold gasket is seating and not leaking.
Another place - although I would not suspect it, is the intake/exhaust manifold gasket. This would not be my choice of places to work unless proven to be the problem!
Removing this manifold assembyl can be tricky, you do not want to break it! Exhaust side can be brittle.

Does the Starting engine fire after a couple of pulls on the crank? Have you tried pulling the plugs - with an oil can, drop some oil/gas mix to the cylinders (like 2 cylce mix) and see if it fires right off when you crank it.

Do you fill the carb, shut off the fuel at the tank, choke, pull it through a couple of times, release choke and crank, it fires right off?
Open the Throttle wide open, dont try to start at an idle, see if that helps.

Based upon what you have said here, it runs properly at idle, so you have checked and double checked spark from the magneto to the plugs.

What do the spark plugs look like? You have run it a few times - are they black or clean? Black indicates too rich which I doubt is the case.

Long range diagnosis is not great, I do not know what else to offer to try to help you through this starting engine headache. They can be plain cantankerous!

CTS

After the cleaning it starts up pretty quick now couple cranks when cold when it's warmer that's a bit tricky since it doesn't want full choke. I am letting it fill and shutting it off then turning back on the fuel when running as you previously recommended and that seems to help more now that the cleaning has been done. 

Tomorrow I will try and wittle a larger stick to stuff that hole closed and I also ordered a rebuild kit for the carb. I noticed a little bit of gas coming through one side when i just tried again before dinner. Seems my skills with permatex gasket maker are not up to par. Between that and the exhaust manifold hole its most likely whats causing the issue. I should be able to get the big motor turned over with a second set of hands helping at least and get this guy his trailer back.

I haven't checked the spark plugs again since I put the new ones in but highly doubt the issue is there. Motor runs strong when controlling the air by hand and it wouldn't be if I didn't have proper spark. Went through trouble with electrical on my jd 40c so after buying a new carb only needing points and condensors I now start with electrical instead of fuel haha

Might pull the carb off again in the morning and scrape off that gasket and try and make another and see if it will help until the rebuild kit comes, would much rather have the real gasket