Hey, I actually remembered to take a look at my early frame rails. Not surprisingly they don't match the book. This info may also help answer the following thread:
http://www.hipomustang.com/hpmx/topic.asp?TOPIC_ID=5899
The access hole is 3.5" forward of the shackle, with nothing in between, and nothing behind the shackle. There is a reinforcement plate just forward of the access hole, but it is for the tie-down bracket (mine are still on the car). This is fortunate because the rail is badly corroded there and the thick bracket and plate are probably holding things together!
The tie-down bracket's rear-most hole is 1.75" forward of the center of the frame-rail hole. The middle hole is about 2.75" from the center of the frame-rail hole. The forward-most hole for the tie-down is 4.25" forward of the center of the frame-rail hole.
Note: Tie-down has 2 holes on the side of the frame rail and one threaded one on the bottom. (see this old pic, front is to left:)
http://hometown.aol.com/misterend/images/lhang.jpg
The early-style tailpipe hanger for transverse exhaust is mounted 8" forward of the frame-rail hole. Other than the holes I mentioned, there is nothing else.
One other thing I noticed is that the shackle mount looks a little different than the pictures of I have seen. It looks like it was built as a complete bracket, with a flat part that mounts to the trunk floor. The rear frame rail has cutout areas on the sides that go loosely around the tubular parts of the shackle bracket. The photos that I have seen of replacement frame rails all look like the bracket and frame rail are more integral.
I am absolutely positive that my rails are original, and that my car is an October '64 Hipo. I think Gerald ("65Hipo") has an early transverse car, too. I'll try to take some photos and link them here.
Lyle