Here is my two cents on this, after doing alot of asking about this here and other places.
I have filled my block to a little above the freeze plugs (SB). I decided against the oil cooler from the get go since I have a street car and unless the coolers are thermostatically controlled, it can take quite a while to heat that oil up. So I am putting a temperature gauge in the pan, and will watch my oil temps, then decide from there if I need to add a cooler to the system.
Consensus is a half fill should be fine...and remember what you need to watch is oil temps, not water...if anything, your water temps should be better than before since there is now less area for the water to cool...so don't be tricked that cooler water means cooler oil, because it doesn't
Thats my
...good luck!