I’ve done the 6 speed tranny fluid but not dropped the pan on a dodge 4 Speed yet.
I agree oem mopar parts is way to go if not crazy price; guaranteed proper fit worth a little more money IMO.
AMF+4 in jugs a little cheaper, if not dealer then good after market brand Iike Castrol.
Buy extra fluid; I like to use manual suction pump a few days after pan drop and replace another 4 litres. Hose fed down through dipstick and it only takes 10 mins to remove used oil. Now most oil is changed out.
4 speed uses pan gasket not silicone, so no over night drying needed, also kinda nice.
If pan-has a little donut shaped magnet , clean it off and reuse it. Use 1/4” ratchet and don’t over torque those little fastners, use torque wrench if you have one, approx setting 100 inch pounds.
Make sure to clean off surface where pan gasket goes, scotch bright or sandpaper to remove all of old gasket. After oil change and truck started, shift through all gears then back to park. Read dip stick info, it may say to measure fluid in neutral, use parking brake. Fluid temp matters, H for hot or full engine temperature. Low level can cause cavitation, damage tranny, accurate level matters.
Messy job....good luck.
No dipstick for the 6 speed is no big deal. Dorman sells a dipstick with markings on it and a temperature chart. I think rockauto sells it still. Pics of dipstick kit and cheapo Harbour Freight type oil suction pump, very handy $15 item.