I did that several years ago and it works well. The OE TJ front turn signal bulb enclosures fit the JK light enclosures perfectly, no modifications needed.
One hint... see those three notches cut in the top photo? Those allow you to insert the JK bulb enclosures and lock them in place by a twist-lock. Cut the three notches so they are clocked at an angle so the JK enclosure will be straight when twisted to lock them. You also need to cut a skinny sheet-metal width notch into the three plastic ribs on the JK enclosure at the very front so they'll be locked into place.
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