I need a new radiator, oil pan, and rear man seal... How do I order the right parts...I just bought this pickup and don't know much about old vehicles....this is a learning experience for me

Has a 351w, not the original motor (I don't think), 4wd, manual 4speed

Current oil pan pn is D5UE-6675-BA

 

Anywhere you order they will want to know the make, year, and engine size (and the trans type for the rad).
Knowing the year of the motor could be important for the rear main seal (early style and later style) and is good to know regarding the oilpan.
If all else fails, there should be a part number for the engine block kinda behind the starter
That should be all you need to know.