We had a mid 80s Lebaron hatchback, I can tell you without a doubt that hatch weighs a lot more then any 30s or 40s trunk lid, even the huge business coupe lids.

That said, you probably will want a longer one, its a long reach from closed to open, you will have more mounting options with a longer cylinder. Mounting locations are going to be the trick to having a smooth opperation, and I suspect you will have to do some trial and error to get it right. The factory used a prop rod type thing. The long arm mounted between the trunk frame and the lid and it expanded until a little lever locked it open, you lifted past the lock point then lowered the lid a few inches to set on the lock. To close the lid, you lifted past the lock point, and the lock released so you could lower the lid. Often you had to lift past the lock point a couple times before it would lock or unlock so you could hold it open or close it. Pretty neat little deal, but could get frustrating. Hard to find ones that still work, so that must have been an issue through the years. Gene