Jay, 1). The bonnet locks on my BEX494 have the hinge towards the windscreen. They left witness marks in the aluminum so it wasnt hard to tell how they mounted.
2). Weatherstripping is usually on the door, and on the body for the boot & bonnet, BUT, you'll see it both ways. My door seals are on the body as I couldnt keep them attached to the door especially under the front top edge that "slides over" the cowling on each side as you close the door.
3). I hand cut rubber gaskets for the taillights and like them better than any repo's I've seen.
4). Cant really answer your question, except to say that windshield wiper units are readily avail & fairly cheap. An MGA unit should interchange.
Seasons Greetings,,,,,,,,,,,,,,,,,Bernie