Re: Can a JackPlate be used for this ?
Filling the holes isn't so bad. Make sure they're clean with good fresh wood surface inside. You might have to drill to the next size. Then cut dowels about 1/2" short of flush of the transom. Coat the hole and the plug with Ultra Silicone, shove the plug in so it's centered inside the transom, then fill the holes and form caps with more Ultra Silicone. There are several colors of Ultra Silicone. Buy something close. The holes are going to be between the clamp brackets and out of sight anyhow, except the front top two in the motorwell. About ten bucks altogether and you don't hardly need much of it. Don't use regular silicone. UV gets to it.
Problem with using a jackplate usually involves the steering cable and how offsetting the motor back affects cable routing. Can the motor still be reached without any radical bends in the cable? Will you need a longer cable? If you were upgrading to hydraulic steering anyhow, then routing isn't a problem. But that's abuncha $$$. Is the transom strong enough?