D4 7U oil clutch question

I have a D4 7U #35424 I bought it to do some clearing/leveling on small blueberry farm. It has had a hard life and needs some bottom rollers and that triangle part that attaches to the hydraulic piston to lift the blade is cracked and needs gauges etc. but it seems to run ok. Anyway, I started to change the fluids on everything and when I got to the clutch I'm not real sure what kind I have. First off, I did convert to 24v direct start. When I took to cover off of the flywheel to install the starter, I could see the flywheel and it did appear to have some rust on it and no oil residue. Now when I crawled under the tractor,I found the drain plug- is few inches wide with 4 or five bolts around the outside and a hole in the center where either a bolt snapped off? Or is there supposed to be an open hole there? On top by firewall there is a small fill cup of left side but on right side where the dipstick is supposed to be for the oil clutch there is a small cover plate. So it seems that it is a dry clutch? I thought that the 4 or 5 bolt drain plug had a screen in there for the oil pump for clutch so I'm not sure- any insight would help.
Seems to run and shift okay. It did have a lot of water in the transmission. So probably had sat outside for a long time. Also, any ideas where to get maybe some used rollers? I am in south New Jersey-

Lat D4's, 7U29734 use a plate with a smaller drain plug and gasket as you describe. Your choice as to leave the drain plug out. Nothing to do with a oil clutch.

Thank you, that helps. Next is gauges and adjusting the brakes but the those long adjuster bolts seem to be frozen up pretty good -did a few searches on here and found some good techniques we will see-

the top of one of my brake adjuster bolt was snapped off when i bought it---trying to get it free without that bolt is tough---don't overdue them and twist it off!!