The drop down gate came on factory soft top cruisers. It is rarer than the swing out gates, and price depends on the condition.
There is work on making factory replica drop down gates and from what I understand they should hit the market soon. When that happens the price for the real ones will probably come way down, I think they go for way too much on ebay as is.
If your cruiser has that now, I would leave it that way. It requires quite a bit of drilling and such to switch over to the other kind. Personally I like the drop down gates, but that is just my opinion.
I believe only softtops came with the drop down tailgate, not sure. I wouldnt worry about that as far as determining what its worth. should be able to get a 70 in decent driving shape for 2 or 3,000
depends what you like as far as which style doors.
you can always change to swing outs if you dont like the drop down. what I like about the swing outs is theyre different--they didnt put them on heeps
While most if not all US factory soft tops get the swing down tailgate, non-US soft tops can be had with half doors (type B) or ambulance doors (type C). Some hardtops come with swing down tailgates too.
From just looking at the tailgate, my answer is no, you should not have any sealing problems. I wonder if you can still purchase weatherstriping for the tailgates tho? I know you can for the swingouts.