Mounting heads: bolts or screws?

[Krumelur]

I ordered a new Jabsco Comfort Quiet Flush Electric head back in November 2021 and it's still due for delivery.
Meanwhile I consider switching to a Johnson Aqua T Silent. It's about half the price and seems to be about same level of quality.

However, the mountings won't fit. The big question is how to properly mount the new head? Can I use wood screws or do I need to (how???) get bolts into the head's pedestal (this is on a Bav 40 and we're talking about the aft heads)?

[tiger79]

Remove one of the existing bolts/screws and see what type it is.  It's possible that there's an aluminium plate bonded to the underside of the GRP, with bolts threaded into it.