No, don't listen to any of that. Needle position on a dial cord was never designed to be moved around. EVERY dial cord has exacting specifications such as length etc. but the M70 dial cord isn't even physically attached to the needle. Instead a nylon block is attached to the cord. The needle just floats freely on the front panel screen. When assembling the chassis to the front cabinet, the backside of needle is a bent piece of tin with a couple of flanges that matches the nylon block, and assembled correctly, allows the block to nest within those flanges. Therefore, the moving block pushes or pulls the needle along the dial.
You may think that an incorrect needle position must mean that it is installed in the incorrect position. This is not so. The reason the needle is off is because the FM band tracking circuitry if out of adjustment. Therefore this is an ELECTRICAL adjustment and not a MECHANICAL adjustment.
To illustrate via a car analogy:
Your car front end alignment is off. On every car front suspension, there are numerous tie rods, ball joints, idler arm, pitman arm, drag link, etc. Changes to tolerances, geometry, etc due to wear, accident, improper adjustment, etc. will throw off your alignment. This can cause tire camber angle (vertical), toe (distance between tire centerline on front vs rear), and caster (steering angle), etc. But it can also cause your steering wheel to become off center. To remove a needle and reaffix it to where you think it should be would be akin to removing a steering wheel, and putting it back in a different spot. Yes, shadetree mechanics have been doing that forever. No, it's not the right way to fix it. The correct way would be to align the front end.
The correct way to fix a tuner needle position is to align the tuner's circuitry. Note that band tracking circuitry also often affects the band coverage too. In other words, you might notice that the needle is off at 92.1 because that's where your favorite station is located. It's also possible that the needle at 106.5 is spot on or even far worse off. Moving the needle therefore only makes it accurate at the spot you moved it. Yet, the tracking is still off.
Now the bad news: I don't see a service procedure included in the SM for the M70 for tuner tracking. It is included in tuner adjustment instructions for virtually every tuner, or sets that include a tuner. Luckily M70 tuners have proven to be fairly reliable, unlike Sanyos that seems to always need fixing. Can it still be adjusted? Most certainly, but you'll need a specialist who knows what coil to tweak. Indiscriminately playing with the coils will most likely lead to irreversible damage to the alignment. In the end, I suggest you just leave it alone. 1/4" off isn't that much, and it's not like you don't know what station you are listening to. Most folks know exactly what station is playing the moment it is captured while turning the dial.
Lastly, Transistorized is incorrect in that the tuner needle would be lined up at the factory and glued. In fact, every tuner cord and needle locator is certainly built on a jig based on specifications. Therefore, they are all identical and a used cord from a different boombox installed in any other boombox of the same model should still locate the needle in the exact same spot. Additionally, the tuner boards are probably electronically aligned on another jig which duplicates the needle positions based on the varicap wagon wheel position. I'm sure that if any discrepencies manifest after everything is assembled together, further alignment "in the box" is conducted until within tolerance.
Mechanically speaking, the tuner needle should rest at 88 MHz on the low end, and 108 MHz on the high end, and travels between these extremes. If you moved it 3 MHz to the right, it will now be parked at 88.3 MHz on the low end and travel past the scale to 108.3 MHz on the high end. If you understand this, then you'll also understand why any changes need to be performed electrically and not mechanically. It's not the needle that needs moving. It's the tuner is not electrically tuned to the proper frequency to match the needle position.