I was meaning "arms distance" or about 2-3 feet when I stated normal viewing distance for 8x10. At that distance, you don't necessarily see the individual grains, but you can see that it's got grain, which you may not notice from a similar print made from a 120 negative.
Anyway, by the time we're looking at prints in excess of a meter in size, the difference between a 35mm and larger negative print will be pretty obvious even at 2 meters away. Plus prints of those sizes aren't cheap or easy to make. So a lot of potential buyers will balk at paying a fair price for a fuzzy photograph, unless of course, the grain itself is part of the aesthetic. Galleries know this and may not want to show your piece if it doesn't have the potential to generate enough money to justify how much space it takes up. So if you're going to go through all of the hassle and cost to print at that size, I'd recommend using a higher resolution format unless the grain and fuzziness is intentional.
Of course every situation is different, and there are no rules in art that can't be broken. But speaking from personal experience, I've entered 8x10 prints of good quality made from 35mm negatives into photo contests before and have been told by judges that my compositions were great, but the lack of sharpness held me back. I don't agree with their mindset, but I can see what they're seeing.