Tee Hee, "BTW early gaskets except the aluminum trim, later gaskets accept" pedant, beat me to it.

Pete

I would strongly advise using a new 'screen seal
Then I would put 3M non-setting black windscreen sealer in the groove that hold the windscreen. My personal preference is to put the welded rubber join in the rubber at the bottom centre. Whatever you do centre that joint either top or bottom.
You then fit a cord into the lip that holds the rubber into the aperture in the bottom. Don't use too thin a string it will rip the seal once the windscreen is nearly home. I would advise putting it in so that you have the two loose ends at the bottom centre. You then place the whole shooting match onto the car, making sure the cord ends are both inside. At this point it is important that you centre the 'screen from left to right. It is possible to do the job on your own but I would advise a helper if you haven't done it before.
You then apply GENTLE hand pressure to the screen; you'll only rip the seal if you get forceful. You then pull one end of the cord, slightly up, pulling the lip into the car. As you apply pressure to the screen GENTLY persuade it downwards. Stop when you have gone just past the corner and do the same for the other side. Make sure the screen is settled well down and EVEN from left to right. Then pull the rest of the seal into the aperture. Look inside the car to see the lip is even. Now pump in lots of the black goo, a bit of masking tap at this point makes cleaning up easier but the stuff shouldn't damage paintwork.
You then go round and press the seal down until it is properly settled. If the screen isn't properly centred you will find that as you work your way round the bottom corners alternatively pop up leaving a gap twixt body and seal. Once again make sure the lip inside the car is even.
The outside trim is a B****rd to fit. It is important however and it has to be done last. It actually expands the rubber slightly to provide the final seal. There are different schools of thought on this, but I prefer to fit the trim dry without lubrication. If you lubricate the rubber the trim pops out of the seal faster than I can fit it. Fit your rope into the lip the trim goes into forcing it as far into the lip as possible. You then have the lip standing proud. You then get the trim and hook it into the bottom lip then gently twist so the top is also engaging with the rubber. You then pull the trim to the outside of the car so that the vertical part engages with the rubber. At this stage the trick is to get the vertical part to stay in. You then make sure the bottom part is engaged and you start to pull out the string towards the centre of the glass. My personal preference is to work from bottom to top, you use one hand to stop the metal from popping out the other on the string. Once you’ve fitted the bottom part and most of the vertical manipulate the trim into the seal, then to the rest of the trim. When it is half fitted there is actually enough play to pop the rubber into the metal trim with a metal hook if you miss a bit, a thin blunt screwdriver with a bent end something like that.
You then fit the two centre joiners onto the trim you've just fitted sliding them all the way onto the metal. Then fit the other half of the trim, and centre the joiners.