Im always surprised at the number of newer guys that don,t realize that one of the forward facing bolt holes intersects the fuel pump push rod guide hole in the chevy block, IF your not using that hole for the old style front motor mount you need to get a 3/4" 3/8NC bolt with THREAD SEALER on the threads installed in that hole or that hole will puke oil constantly at any rpms over idle speeds,but don,t place one in that threaded hole over 3/4" long or it might bind up the fuel pump push rod
viewtopic.php?f=62&t=1430&p=3168#p3168
the threaded hole might have been plugged with paint, a bolt or sealant that just is no longer there, I have seen several blocks with that hole plugged with a thumb full of silicone thats been painted over, and theres was rather obviously no bolt sealing it, but a 3/4" 3/8"NC bolt with sealant on the threads and a star lock washer is really required if your doing it correctly