Jay, I'm guessing that the "blade or stud" he is referring to is probably metal embedded in the concrete. Some sort of knife plate connection. A little clarification may help Steve.
As to your question, it usually is permissible to drill in and epoxy anchors after the fact. Sometimes this can be preferable as it seems like things get hectic on a concrete pour and sometimes anchors get misplaced or forgotten. There is a certain advantage in being able to able to leisurely layout and place anchors a day or two after a pour.
J bolts have a comforting physical aspect, but this is only as good as the placement technique. If the concrete is not consolidated around a J bolt properly there will be voids. This all comes back to your contractor of course and hopefully yours will be diligent. Overall though, I prefer to epoxy things in after the fact, it's much more controllable.
I think that it going to be quite possible to find an after the fact solution to meet your engineering criteria, but I'm sure your engineer will be able to say for sure.
