Coming from WL, that's a very strange question.
Commercial firearms are built to fit a "standard human body proportions"
Unless your individual body meets that "standard" perfectly, the off the shelf firearm will not fit perfectly, or like a glove. It's impossible.
Sometimes, people feel a firearm "fits" them perfectly, because of its weight distribution between their hands when the rifle is shouldered.
If you get "lucky," the very odd time a rifle will come along that has a butt stock to trigger length that is perfect for proper trigger control and weight handling.
Tall people with long necks "generally" prefer very light, short, barreled rifles, with longer butts. Mid size people usually aren't as concerned about such things because the commercial offering is very close to the right proportions to suit their bodies comfortably.
The type of clothing you will be wearing will change the "perfect" status as well.
For instance, if you hunt with a light shirt, a slightly longer butt is needed for "perfect fit"
If you then use that same rifle in the late fall/winter, you will need a shorter butt to accommodate the thickness of your outerwear.
The list gets longer, depending on your headgear, gloves, etc.
The little M85 rifle you mentioned is a sweetheart. I have bought and sold a couple of them over the years, chambered for 223rem/7.62x39, and liked both of them. However, they worked OK, but didn't do the jobs I wanted them to do, as well as I wanted/needed at the time.
The M82 is handy, light, affordable, and with some TLC can be made slick and smooth to operate. The original adjustable triggers are crude at best, and the stock wood leaves a lot to be desired, as it's made from very soft wood, then dyed to look like Walnut.
IMHO, the only way to get a rifle that "fits perfectly" is to get one with an adjustable stock, barrel length just long enough to balance the rifle when it's held in front of you between your hands, which will ensure it balances well when held to the shoulder and when it's being raised to the shoulder. This should ensure the rifle comes up with the sights/scope in line with your "shooting eye."