In all honesty, I don't know the size, I'm sure I could make them both the same and just step one down to the smaller hose. Remember, it's coolant, not exhaust, so the heat factor will be lower.

I'd cut them if I had the tooling on hand, though I despise turning inside threads on SS, and love turning NPT even less (what a bitch to set up)

I do as little plumbing as possible, wasn't aware SS fittings would work... they'd likely be a different grade, would 309 work, or should I go 308?

I believe they're around 3/4 and just over 1/2"