In reply to iusedtoclimb:
I would say you have got a chance, but it depends how much ascent was in your races last year and how good you are.
70 miles and 9000 meters is more than a Bob Graham Round, the normal bench mark of a good training programme for that is 3000m of ascent a week for a few months before hand, and lots of long days on the hill.
If you can get out most weekends for long days on similar terrain to the race, and in a couple of months time can do 7-8 hours with 2 or 3 thousand metres of ascent and feel fresh after it, then I would say you have got a chance.
If your 100 and 70 mile races were fairly flat, then it's a huge step up and I would say would need 6-8 months of effort to get round.