Gear choice decisions

So I have a 340/4 speed/dana setup in my 67 dart. Street/strip car but now its pretty much a street car. Even though it's not raced anymore (Maybe at nostalgia day) I still love steep gears and refuse to get rid of them. Old school ways I guess. My current ratio is 4.56 with a 27 inch tire. After a while of thinking , I'm contemplating putting 4.10s for a ratio. I have 2 questions. 1) will 4.10s make a noticeable difference as far as revving while cruising at 50 mph? ( I know its not going to be drastic but maybe a few hundred RPMs? ) I'm pretty confident that the 4.10s will still provide the low end punch I love. 2) can I fit a taller tire in a factory 1967 dart well? its currently a 255/60 R15. Thank you in advance everyone!!