Mike - For your small-mouth TR3, you will have different seals for the boot lid than the ones shown in the photos above. My "early" 1958 TR3A and all TR2's, TR3s and TR3As up to TS 59999 have a seal thet fits down into a slot. These early cars also has square corners for the seals. Mine came new with one piece straight along the top (just below the fuel filler cap and the rest was a single separate piece that went down one side, across the bottom and up the other side to join with the one across the top. It was held into the slot with contact cement but since I did my restorsation in 1990, the new seals are not glued into place, They stay where they should down into the slots.
As an added point, the length of seal across the top has shrunk about 1/4" and the upper corners may not be as hermetic as they should be. But then, I rarely drive my TR in the rain. This top seal piece is down in the slot and the seal lip is facing towards the rear of the TR. But I can't say if this is correct or not, but I still have the original bits from when the TR was new and I wouldn't have knowingly reversed it.
The seal lip for the other piece is facing outwards on each side and, naturally still as one piece the lip extends outwards at the bottom towards the rear of the TR. On the RHS, this lip half covers the slotted hole for the boot lid stick.