Please help / antifreeze leak

Is it possible that the head bolts are not in the correct holes? Each head requires 20 bolts; 5 short, 4 long, 1 extra long. The shorts go in the bottom. The extra long goes in the second hole from the left on the top row. The other long bolts go in the remaining top row holes. I was such a klutz at this, I made a cardboard engine mock up so that every bolt goes back in the hole it came out of.

Torque the heads sequentially. In order, torque to 30#; then to 60#. In the same order torque to 85# for 273 & 318, 90# for 340 & 360.

There are core plugs at each end of the head. If rusted out or not installed properly, they will leak. The exhaust manifold studs have already been mentioned.