For a straight-up machine shop, I generally use Arlington Automotive Machine, 511 E. Main St., 76010. PM me if you'd like their phone number. They would likely outsource this kind of work to someone else.
For turbo stuff, I usually source my bits from Majestic, also in the mid-cities area. I think you can find their address on this site somewhere if you do a quick search. I no longer have any receipts with the addy or contact info.
I know Day Custom Engine is popular with the local Miata crowd. That shop does work for TDR and built a motor (for a very reasonable price, I might add) for mr brg. This is the shop I'll be using for the bottom end of my replacement engine.
Hope that helps!