There are LOTS of install pics out there for 300Ds, which you could copy. You dont have to use metal tees, but I recommend the nicer plastic ones that are harder and darker than sprinkler plastic ones. you can get them from auto parts stores. make sure to take out enough hose for the tee at the return point or you will end op kinking the coolant line there. my return line just goes over the top near the tranny dipstick and down the line to the helper pump. i didnt get fancy. i also would not do cheapo pollack valves either. spend the money on frybrids or greasecars. one valve failure or leakage can get ugly. most people use 5/8 and/or 3/4 heater hose, and sometimes both. for example, if you put a pex line in the coolant line (HIH), then you might want slightly bigger, but you could do 5/8 for that length back. dont mix and match though, it has to make sense. and once your done, dont be too eager to switch to veggie. let the car warm up all the way, then let the heat absorb into the filters and such, before switch over. and dont idle on the stuff too long (traffic fine, stuck in football game parking lot not as good). my 2 cents.