The brake issue may be that they need to be adjusted. They are manual adjusters on this truck. If memory serves me right the bottoms of the shoes is on an eccentric mount and then in the middle of the shoe there's another adjuster. the wheel cylinder is mounted at about 2 o'clock so look for the bottom shoe adjustment at about 7 o'clock.

The milky hyd. oil is moisture in the oil- flush this asap.
Not sure where the serial # is stamped & not sure you need it- nothing is available for these trucks through forklift channels. These trucks were made in the 50's & no one has parts books that old. I have 2 of these I service & parts are a b*****.

Engine is a continental Y112 or F163- depending on model. Good industrial engine- take 4 quarts oil ( I reccomend SAE 30)- should have by-pass canister style oil filter. Unit should have manual trans (where are the trans levers- up through floor or on steering column?), engine dipstick should be on the opposite side of engine from manifolds, down low, right in the middle of the block.