89_Runner

So here's some history. Blowen motor when purchased. So i ripped it out and put in a motor i had in the garage. It was a block loaded (crank, pistons ext.) Put on a newer head. New gaskets for everything. Get it back in the truck. Got it running. Now when its just sitting there running or with me hitting the throttle under the hood no leaks. But when i go on test drives it starts leaking like no other. It only leaks on the foward left hand side of the block. It seems to be around were the water tube connects to the front cover. But i know thats were coolant is. So i guess im wondering if the front cover might be cracked. Just trying to get an idea so i know were to start working on it. Thanks