here;s an illustration from the isuzu onlineparts site
www.myisuzuparts.com
showing the water pump and also the area that it bolts onto the engine block.
it is a bit of an odd shape as you can see, and while it's centered on the block, it spans both sides and the leak could travel anywhichway.
suggest you do some cleaning up there so you can more accurately tell from whence it comes....
//bc