These are not specific to a 250 but are generally accepted I think.
Oil,Fuel,and Water Pumps: SECURELY to 20-25 ft.lbs
Valve Covers,Push Rod/Lifter Covers:7-8 ft.lbs.
Oil Pan:7-8 ft.lbs. except corner bolts 12-15 ft.lbs.
Don't overtighten and squish any cork gaskets and
make sure all bolt threads and threaded bores are clean.
Also, after running the engine for a while, check for leaks and loose bolts/nuts.
