NHRA rulebooks: '69 or earlier

[Chevy454]

Anyone have any old NHRA rulebooks? I've got '70-72, but am curious as to if '69 and earlier are pretty much the same. I'm betting they are, but just "curious". The part I'm interested in is the wording on the exhaust:

EXHAUST SYSTEM: Exhaust system must be equal to factory equipment per h.p. claimed. Dual exhaust pipes, with mufflers, are permitted. Headers are also accepted, but exhaust must be production type routed through mufflers and tail pipes. All mufflers must be production type and installed in the stock location - may be moved forward if original location was located behind rear axle - with tail pipes extending at least to the rear axle. The main body of any replacement muffler must be at least 18 inches in length. Open bypasses may be used, but mest be installed in front of the muffler and in such manner as to direct exhaust away from the strip, tires, and car body.

That's verbatim from the 3 ('70, '71, '72) book that I have...was it the same in '69? '68?

Thanks!