I will just add that replacing the spring on the old style will most likely lighten the pull, but may or may not give you the crispness and let-off that you desire. More than likely the contact surfaces between the trigger and sear will need to be honed. If you are pretty handy, you can do this yourself. Everything is adjustable on the M70 trigger. You may be able to decrease the pull weight to your likening with the stock spring by simply backing off the jam nuts.
The reason some prefer the original M70 trigger for a wilderness type rifle is the trigger is all open. In the case of box style/enclosed triggers, they can easy accumulate oils and other moisture then freeze when afield. The M70 trigger is simple, very few moving parts and no where for moisture collect.