I was noticing that some people when listing their rear-end ratios they have different ratios for racing and street. Does this mean that the ratio's are very easy to instal?

It depends on what you call easy. If it is a "dropout" style(8 3/4") it is easier to change "pumpkins" with different ratios.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

I was curious because I've put an 8 1/4 axle on which is better than the 7 1/4 that I had previousely except for the ratios. My previous 7 1/4 was a 3.23 ratio non sure-grip unit while the 8 1/4 is a 2.71 ratio sure-grip rear and right now I'm trying to research on axle work. Is a gear swap easier than an axle swap if you know what you're doing, or is axle work actually one of those things that if you haven't learned you ought to leave up to a professional.

p.s.: I'm not talking about swapping rear ratios right now. I'm hoping that in three years I'll be able to do a rebuild on the axle. I'm just wanting to see about the rear ratio thing since I do quite a bit of junkyarding and if I happen to see a better gearing rear end if I should pick up the internal gearing or if it's really worth it. Plus, I am curious about how the racers do it, it seems like it could be quite a pain.

Thanks!

Rearends are difficult to "set-up" because you need special tools and you need to be able to "read" the gear contact pattern and figure-out which things to adjust to get the gear mesh / tooth contact correct.

If you find a good working used rearend assembly that is the type and ratio you want, buy it. Used rearends usually sell for less money then it takes to set one up with a new gear ratio.

As for the racers, most of them run the "drop-out" style rearend. This allow for fast gear ratio changes because the gears are already set-up in the center carrier ("pumpkin") which can be swapped in about 1 hour.
DD
http://www.dutra.org/pictures/parts/8.75-exp-view.jpg

Thanks, if I find another sure-grip axle with better gearing I'll pick it up(we've got touchy winters, sometime they're dry and sometime the snow's high), otherwise I'll get bigger gearing and rebuild it when I've got time (like three years). For some reason the big axles and later Darts are hard to come by.