5/8" barbs

I've been thinking about bumping up my lowly 3/8" tubing to a more respectable size, and I remember a few people talking about having all 5/8" tubing in their system. The problem I've run into though, is that the smallest npt size for 5/8" barbs is 3/8. I know that I could probably make that fit in my heatercore with some drilling/coaxing but how would I go about getting 5/8" barbs into a waterblock? Would I have to just tap the hole bigger? Please share your thoughts!

Bump!

well unless the block was designed for 5/8" inlet the water is just going to hit the top of the walls anyway so you might as well just reduce the line to 1/2" right before entering/leaving the block.