No Bronze Guides, Any Reason?

I got ferrea 5000 series for my 516 heads. I was thinking of using bronze guides
I found these mahle 2173193 ones but they are .343.
Are they to be reamed to size? I couldn't see any .3745.
Do most shops do reaming spiraling and honing of the guides?
If the shop doesnt have a Sunnen like this should I look elsewhere?
thanks!

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