I would agree, with the below, for roads, might consider a grader, or a tractor equipped with a heavy duty box blade or similar.
For the pond, by your mention of a dragline or clamshell, obviously you know thats no place for a dozer, even an LGP, unless it dries considerably, thats a tough call, there are long reach excavators out there for this work. These size track type tractors are heavy and will certainly sink in soft ground, which I know from experience.
I do recall that there were quite a few D7's going reasonably on government auctions in the past, but its been quite some time, they were around 10K each, low hours, but as is, and the buyer has to determine what they are getting into, some can be cannibalized or similar. I think I saw a really nice surplus D7G, almost N.O.S. on ebay, but he wanted like $195,000.00, that kind of money, though they were good tractors, I'd have to go for something much newer.
If my memory serves me correct, or it was close to the E series D7, on some of those, there may be a concern with the transmission, one series may be more desirable than the other, in that era mid/late 60's, I just do not recall the details, I believe both were power shift, the direct drive models with oil clutches were always just about bullet proof.