Hi,
Most that I've seen without a mount are installed on the front edge of the hard top.
Maybe consider filling in the holes with 5200 and make sure the void is 100% filled and bottom. The coring is likely balsa in the hardtop, so you want to ensure water does not get in.
If you want to mount in the same location, maybe look either for a small mount or potentially a wedge that will give you the proper angle to pick up objects in front of you.
My 282 did not have a mount, it was mounted on the front edge of the hardtop with (4) bolts. My current boat has a small mount. I wanted a bit more height as well as a nice mount to get the GPS sensor out of the radar beam.
Prob best to see some other boats and determine the look and features you want and then search the net to see what mounts are offered.