The rules do not allow modified suspension on '75/'76 models even though back in '75, '76 & '77 there were heaps of bikes with modified LTR. Go figure! So unless you can buy 600mm shocks with 9" travel
The generally accepted interpretation, we think, (what a wonderful way to write rules) of the rules as far as
carry over follow on ( now reads much better) models is that it effectively makes a '75 CR125M into a '74 models as far as the rules are concerned. The intent of the rules seems to be to exclude Pre75 bikes from Pre78 so if the '75 CR125M is deemed a Pre75 bike it, by association, is out of Pre78.
13.14.5.2 Front wheel travel will not exceed 229mm
(9 inches) rear wheel travel will be limited
to 229mm (9 inches) measured at the
axle.
Rear shock absorbers will be in
the original position using the original
mounting points