Water in trunk after heavy rain

maybe i can help as mine idid the same thing...the 69 i have and the car you have are the same besides the tail section...windows and roof are even the same....my roof came from a 74. If it has a vinyl top there will be clips in there for the trim piece closest to the trunk......and they are notorious for collecting water and making pin holes..,...and covering rust

There is also the stainless trim that goes around the back windshield...the clips there also rust out.....after the water sits on the paint there for years

with the vinyl its worse because the vinyl from the factory was porous and saturated every time it rained it got wet...it was the paint underneath the vinyl that protected the metal...when the water finally cuts through the paint...it creates the hole.....water is like really fine sand paper. vibrations from the car make it sand your paint in areas where water sits....good paint is key....primer back then as well as now is like a sponge and does not protect the metal underneath...it makes the situation worse.....

Epoxy primer is water proof and is all i use

my leak was coming in through the back window channel at one of the clips and under the vinyl....i could not see it with the flashlight method. when i took the windshield out...it was very rusted.....even with the trim piece off the car...the clip covered the hole and the flashlight didnt work....i had to replace and make a piece to fit.

also with the vinyl top i had.....it created the holes on the lower end under the back windshield....the vinyl top covered the holes and the flashlight method did not work there either....

the trunk lip is really tall and is probably not the problem...even if the seals were bad the lip would keep water out

by the time i fixed it.....it had trashed the trunk.....gas tank (on the top of the tank it rusted through and the rust got in the gas) ....inner quarters.....outer quarters....and trunk extensions

back window seals are very easy to fix compared to all the sheet metal work i had to do to make it water proof......

i removed the glass with a non smooth guitar string.....or the tool you can buy.....cleaned up the glass which is tempered and not nearly as bad as a windshield.....put the seal around it and glued it back in with windshield glue and a new seal......painted the area i replaced and have not had a problem since. I always put 4 coats of paint and clear in these areas that are where the water is naturally going to flow and where it is going to sit.....like the lower front door jambs and window channels.....sorry so long winded....hope it helps

on an after thought.....my problem right now is in the front of the car.....over the years, dirt and leaves have gotten into my air inlet grill under the windshield and stayed there around the towers on each end that keep water from entering the air ducts on the driver and passenger side.....the rain and dirt ate that area out....i have to cut it all out and replace it under the panel the windshield wipers sit on......what a mess...i think from now on after its fixed and painted in there i will force high pressure water in there to make sure it stays clean...it sat under a tree for years.....by the time i cleaned it out....caked dirt came out.....i took the fenders off and the drain hole was clogged on each side....just a side note to look out for.....it trashed my carpet.....heater duct towers under the panel...... and is on its way to the floor boards....

ill post pictures of the repair and the damage when i tear into it....