<< I'm trying to attach some wood structures to a block wall. They will have
about 50 lbs. of weight. >>
Here's what I did to mount a big electric service panel a while back:
Drilled 1/2 " holes at the mounting screw locations. Used 1/2" maple dowels and
epoxied them into the holes, and drilled pilot holes for the screws in the
dowels. Inspector checked the set up, broke off a fingernail on some epoxy
dribbles on the block, laughed and said something like, "That ought to last a
while" and we hung the unit and screwed it down tight.
Something like that might work for you. Tapcons are good but they have a
tendency to crack softer concrete such as blocks.