Coolant in oil; head gasket looks fine?

First time poster, new owner of a '91 Mazda B2200. I've had the vehicle for about a month now and a couple weeks ago out of no where began seeing a lot of white smoke and high running temperatures. Condensation under the oil cap, milky substance in oil.. thought I had a blown head gasket for sure. When draining the oil it was quite obvious it had a BUNCH of coolant in it, so I was expecting to find a very obviously failure once I pulled the head off. However, I did not. Head gasket did not appear to have failed catastrophically anywhere, and now I'm at a loss as to how the coolant ended up in the oil. Checked the head for warpage and its damn near perfect, what else should I be checking? Is it possible that the coolant was getting past the head gasket without a discernable failure on it anywhere?

Cracked head possibly

I just did my head gasket. It blew between 3 and 4 but it was pretty noticeable. I would go with squidlips and check for cracks.

A visual inspection of the head didnt turn up any cracks, but thats certainly not a definitive answer. Everyone I have talked to with any knowledge of B Series has said that the heads on them almost never go, but that it certainly could have happened. Now I'm starting to think I would be best served getting a head from a boneyard as opposed to paying to have this old one tested at a machine shop. Any suggestions on that front?

You could have an internal crack which wouldn't appear at the surface. If the machine shop did a thorough job of checking out the head they would have disassembled it and pressure checked it. Maybe you just got a quickie job. It's likely all you have to do at this point is put a new head gasket on it and keep your fingers crossed. Maybe all you had were loose head bolts. They loose tension due to stretching. Head gaskets fail in a lot of ways. How many miles are on the truck?

Truck has 107k, the guy I purchased it from claims the engine was rebuilt 16k ago. Maybe I wasnt clear, but I did not take the head into a machine shop yet. Was kinda debating the merits of having it tested VS getting my hands on a different one.

All that probably happened is that the head wasn't re-torqued after the rebuild. That is almost sure to cause premature failure. I'd stand by my original statement and just throw a new head gasket at it.

The bolts did seem to come off awfully friggin easy when I disassembled the thing, I'd just hate to put it back together and still have the problem, although I guess it would be a lot easier to do the second time around haha. I'm gonna roll the dice and put er back together with the new gasket and hope for the best, thank you for all of the input.

"The bolts did seem to come off awfully friggin easy when I disassembled the thing,"

When I disassembled my B2200 engine (at 183K miles) the head bolts were REAL hard to loosen/remove. I absolutely used 1/2 inch drive socket, and cannot remember if I used breaker bar, breaker bar plus extension, or my 1/2 drive Harbor Freight electric impact wrench to loosen. Rest assured: I did check torque/re-torque at about 550 miles, remember three of the ten bolts needed a tweak of tightening. 24K since that rebuild....

You have a crack some where that is causing the leak into your oil. The crack in my cylinder head was in the number one cylinder between the intake and exhaust valve.