[Blackeagle]

I would say stick with your first order rad=>block=>res=>pump=>rad Use 5/8" lines from rad to block and block to res if you like instead of the 1/2" you first listed. Then use 3/4" from res to pump and pump to rad if you want, but 5/8" would give the same results with that size of pump. Unloaded is right about discussions dealing with larger lines, most of all at the inlet. But lines larger than 5/8" are only usually used for the biggest of the Little Giant and Iwaki pumps. And what are the inlet/outlet's ID sizes on that pump, I'll bet they are 1/2" or at most 5/8" ID. You don't really want to have to add a reducer fitting at the inlet & then a second fitting at the pump to go back up to 3/4". 5/8" can most likly be clamped onto barbs of 1/2" ID without any problems and no added fittings. And 5/8" ID can be stretched onto the 3/4" inlet at the rad with a little effort or a bit of warming as Unloaded mentioned.

Reason I'd go pump, rad, block instead of rad, pump, block is this: The pump itself adds a slight amount of heat to the water, not much but it is there. By haveing the rad after the pump & before the block allows the rad to remove that pump heat, while all the pump heat will go to the block if the rad is before the pump. The differance gained in this order is not great. But if you can so order it without lengthening your lines then may as well get all the little gains you can.