Figure the availability of parts and service for the old machine, plus wear and tear, plus down time when some unavailable replacement part breaks, and money ill-spent on repairs, and i think you will see that a newer or new machine, with its inherent ease of starting, availability of parts and service, will be the better idea!
A friend has a newer Craftsman snow blower/thrower, and he uses it to plow snow on his paved lane, and he has had no troubles with it. Note that he takes very good care of it, and it runs good as new, and looks new, too. He does all of the maintenance on it. I think it is at least 4 years old. Doesn't have any problems with it--and it starts readily, no matter when he tries it. An ancient machine will keep you busy seeking parts, if it breaks down, and other problems will surface. Peace of mind is essential. and struggling with a balky snow thrower/blower, on a cold dark night, or in the daytime, will soon have visions of sugar-plums, and a double-header of Scotch, dancing in your head!
Go NEW!!

amen, rusty...

if it is in good shape and has been well taken care of i would go for it. Most older machines(if they are taken care of) will last forever and out-perform the new ones.

I bought a used Gravely two wheel tractor 30 years ago. It has a 30 inch mower deck, a 48 inch mower deck, and a snow blower. I used it to mow two acres of grass for ten years until I got a fifty two inch ZTR mower. I still use the Gravely for snow blowing. The only expense I have is buying a battery every few years. You can still get parts. I don't think the design has changed in 50 years.

Now I am confused. Does the gravely throw snow better? I find it hard to believe an attachment for a 30 year old machine would work better than a machine made just for snowblowing with new technology...if there is such a thing as changed technology on a snowblower.

Rusty / Rcbe: I'll second that and this Beers for you Dudes !

Mower: I think it all goes back to Parts availability and your technical abilities Bro ! If the Unit was a Reliable Model and in a good state of repair , you may be happy , if not , Reverse Engineering Parts is costly and Time Consuming. I would go the "kiss" Route unless your Handy :)

Below is link to photo of a Gravely with snow blower on sale at e-bay for $800 that is just like my 50 year old machine. I inspected the gear box on this equipment and it looks just like the gear box on a Ford Model 'T'. It has two fly wheels, each with a steel band that clamps around the fly wheel to engage forward and reverse.

http://cgi.ebay.com/Gravely-Commercial-10a-w-snow-blower-attachment_W0QQitemZ320477724137QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item4a9df5fde9

Here is a link that might be useful: snow blower

I think I have figured out the way to run old stuff. I have 2 old Ariens sno throwers that are pretty much identical. I run one until it fails, then I switch to the other. So far, so good. My drive way is 125' long plus a turn around. I once had a larger Ariens, but when the impeller shaft broke, I relegated it to spare parts. It was beating me up trying to manuever it. The smaller units are way easier to operate. The old stuff is made from steel, not plastic. That is why so many of them are still around.

The Gravely two-wheeled tractors are fine machines, but they won't throw snow further than a modern two-stage blower will.

They will however, be around and working years from now with proper care.

There are lots of YouTube clips of Gravely two-wheeled tractors running a variety of attachments that were available as accessories when the machine were sold new. There are even a few clips of homemade attachments out there.

Here's one of the snowblower videos:

Here is a link that might be useful: Gravely. Many more to view off to the right!

I agree with Rusty.
If your used lawn mower breaks down ,no problem, just mow the taller grass when you get the mower fixed.
If your used blower breaks down during a major storm ,your screwed.