Kohler Quitting

I have a Kohler 321 in my Case 644 I'm having an issue with
The output shaft is hooked to a hydraulic pump and I haven't used the attachment pulley.

I got the 644 a few months back and have been slowly fixing issues as they come up. Its now mostly functional and when the engine runs properly it runs great. I ran it for a good 6 hours straight two weeks ago, then the next day it ran not as good. Doesn't use any oil, and the level is right at halfway on the stick.

I ended up swapping the oil pan for another identical one this weekend -- the previous owner stripped out both bolt holes on one side. Its now mounted properly, but an issue I noticed a little before is now much worse

It'll quit without any real rhyme or reason, most of the time like I just turned the key off. It'll then start right back up like nothing happened. Sometimes it'll sputter for a second before it dies, and if I flip the choke up it'll splutter for a few more seconds before it dies, but there's no saving it. Again, immediately after it dies it'll start back up.

Where before it did this once in a blue moon, now I can't leave it idle for more than 2 min or so before it dies off.

I replaced the fuel pump hoping that would solve it, but no go.
Next step I guess would be the carb, ideas?

Thanks!