Okay I have my 399069 heatercore ($16.99

), but I have a few questions. I have a Z4 waterblock, a Danner Mag 3 pump (I think) & I am making a res (the pump will not be in it, it will probably be the size of a cut down and skinnier quart of milk). I will be going rad>block>res>pump>back to rad (not set in stone).
1. The rad has 5/8" inlet & 3/4" outlet, does it matter which one I use as inlet or outlet?
2. I was thinking that the larger diameter would be good, am I wrong, should I cut them and attach 1/2" ID barb?
3. I am using 1/2" ID Tygon, if I fit this over the larger opening does this pose any potential problems?
4. If I use the stock openings to what should I have the 3/4" going/coming to/from?