1973 ford maverick 302ci stop turning over?

I bought the ford for 125 dollars, it wasn't running then for about 5 years so i got it running a while ago then i let it sit for about a month( don't know why) and today i got it running again and i heard a knocking which sound like it was coming more from the top of the motor, i though maybe the valves, so i would let it idle for a bit and it would still knock but it wouldn't knock when i would rev it( i also added seafoam in the oil after i heard it knock because i was about to change the oil) so while i was driving it, i decide to go out in my field and do a few donuts and i push the clutch in and ended up reving it hard so i let off the gas and it died and when i tried starting it all i would hear is one click from the starter, its a 3 speed and i can shift it though all gears but when i put it in first and tried moving it, it wouldn't move at all, so what happen, and their was a milky color in the oil.