If not built correctly, an FE (new or old block) can leak in several different spots. The whole engine is a unique design, with the intake making up part of the valve cover flange. If the intake is not perfectly aligned, then you will get a valve cover leak.
If certain intake gaskets are used, then it's possible to get a coolant leak into the heads.
The rear main seal is also a trouble spot as there are two seal halves, along with side seals, since the block is a skirted design. Different windage trays and
oil pans can also play havoc here as they block the return in the rear main cap.
All of these things need to be watched carefully upon assembly. Otherwise it's smooth sailing.