Timing Chain Cover crankshaft opening is the wrong size

fulltank said
I bought a new timing chain cover and I thought I had the right one as the timing marks lined up on the drivers side but as it turns out the new opening for the crank shaft is larger than the original, will it still work ? or am I better off getting another one that is the same size opening as the original. I never realized there were so many variations . This is a 68 LA 318 engine, in my Dart. When it was rebuilt they used a 73 318 block but kept the 1968 components, the water pump is the original 68 style. The timing cover rotted out from coolant corrosion so I have to change it all out . I read some of the install process on the forum but didn't come across this scenario tks.

Okay, first off if you have timing marks on the driver's side, it's not a '68 318 timing cover. A '68 front cover will use a cast iron water pump with a driver's side inlet. With driver's side timing marks, it should be using the later aluminum water pump with a passenger side inlet. using the wrong pump on the wrong timing cover will hide your timing marks behind the loser radiator hose and pump inlet, making them very near unusable. Not to mention the fact that if the timing covers were swapped, your balancer needs to have it's timing mark relocated, since it will be nearly 90* off with the timing marks switching sides.