mossie,
Since no one else has responded, I'll take a shot. I have a small dozer (Case 450 C), a front-end loader/backhoe, and tractors and have scratched out a couple of ponds in East Texas.
Can you accomplish what you want with your equipment? My guess is yes, given lots of time and patience. You should plan on doing the work in dry weather, otherwise you won't be able to move the dirt and run a significant risk of getting equipment stuck/bogged down. Presumably you can use the bucket as a psuedo-blade and push dirt when you need to. When you are working in the clay, my guess is that it will be very time consuming. Cutting the clay is difficult even with a dozer. Always place safety first.
You mentioned spillways...and my opinion is that natural spillways are the best, cheapest, and longest lasting. That's not generally agreed to, but in a small pond like you are talking about, I wouldn't consider anything but natural spillway. Also, you should probably plan on renting a dozer for the final work.
