Okay, I finally picked up a nice Marlin 39A yesterday but, upon closer inspection, the front sight ramp is mounted very off center. In other words, when sighting down the barrel, the ramp is leaning toward the 11 o'clock position.
At first I thought that maybe the barrel needs to be turned a bit, but the rear dovetail is level with the receiver.
Has anyone encountered this problem before? I don't see a simple fix. Fill the existing holes and drill new holes in the 12 o'clock position?
Any advice would be appreciated.

Many, many years ago I received a Savage .22/410 over and under. The front sight base was mounted off center. I found out why when I shot it. The barrel was off a little and they corrected it by mounting the front sight off center, too.

I don't know if this is your problem, but you might try shooting the rifle before you move the sight.

Jim Luke

Oh man, I hope that's not the case! I planned on putting on a rear aperture and, as it is, the front post would be at an angle in the sight picture.
Thinking more about this...
The previous owner had the rear buckhorn sight moved way to the left in the dovetail. If Marlin intentionally mounted the front sight to the left (presumably because the rifle was shooting left), then it doesn't make sense to have to move the rear sight to the left in the dovetail, which would make the rifle shoot left again.
Does that make sense???

Sounds like a simple machining error. The front sight is mounted left of center, making poi to the right, so the last owner adjusted the mid sight left accordingly. Correcting the front should remedy the situation.
Not ideal, but a simple solution is to mount a lyman 17a drifted to the right side of the front sight base. Again not ideal, but simple.

I had a Winchester 9422 with a canted front sight. I never noticed it until I was at the nationals the morning of the small bore match. I was aware of a windage issue I was experiencing even when the wind wasn’t blowing. Turns out the front sight being out of time was introducing it at the long line.

Life’s too short to compete with a rifle with an incorrectly timed front sight. This isn’t something you can fix. Sell it and buy another. There are millions of 39A’s out there.

So after reading the post by Jim Luke, I took his advice and shot the rifle before doing anything drastic to the sights.
I reinstalled the front and rear sights CENTERED in their respective dovetails and went to the range.
It shoots almost exactly 4 inches to the right at 25 yards.
This tells me that mounting the front sight to the left was not done intentionally to correct a barrel that was shooting left for some reason. It also explains why the previous owner had the rear sight drifted so far to the left.
Drilling & tapping new holes and properly timing the front sight seems like the perfect fix.