New (to me) '93 F250 - What mainenence?
 

I recently bought a 1993 F250 automatic with a 351 gasoline engine. I can tell just by looking at the dipstick it wasn't taken care of all that much by its previous owner. I've already done the following:

• New Air Filter
• Cleaned air intake
• Drained and replaced coolant
• Fixed bad harmonic balancer
• Replaced wippers
• Checked for any OBD-I codes
• Filled power stearing fluid
• Checked brakes/fluid
• Replaced spark plugs/wires

My next move is to change the engine oil and differential fluid. I don't have the manual or any sticker which says what oil to use, and ford.com support only goes from 1996. How much oil does the engine take (I'd imagine 6 qts), and which oil (I am in a warm climate)? Also, I have read to use a 75W-90 for the differential, but all I find in the store is SAE 90 for manual transmittions or ATF fluid. Would the SAE 90 suffice or do I need to look further?

Once I get through with that, I plan to clean the throttle body out. Anything else that I should look over before a current problem becomes worse?

THANKS!