Thanks for the advice.
Hadn't considered moving the engine back in the frame - that's a lot easier than leaving the engine where it is and extending the frame out.
Is there a real benefit to large diameter tires? I know I'd get a better contact patch, all other things equal, but it also seems (again, all other things equal) that I'd loose a lot of torque. Although it looks like, if you want wider tires (which I think would help a lot), then you have to go with larger diameter tires.
Of course, the extra clearance is likely a plus too with the larger tires.
I don't have a bunch of experience with this kind of terrain. The area doesn't drain all that badly, but the soil is mostly clay and gets slick in spots. Although I've cleared a lot of trees, it's still pretty shaded and doesn't dry out quickly either. I guess I'm looking for traction without sinking in or sliding off. Would be a bonus if we could visit the property during the winter.
I tried to take our Sierra uphill (going forwards). Once I lost traction up front, the nose started to drift sideways. I'm guessing this is because the engine is above the axle and up in front and it basically wanted to swing itself around so the heavy end was pointed down. I think getting the engine lower and behind the wheels would mitigate this, at least to a degree - might even help transfer the weight to the back wheels to help traction back there, which is awful on the Sierra. Considered trying to go up backwards, but after we kissed the tree and dented the truck (while pulling it off the side of the driveway with the tractor), my wife decided she really didn't want to go anywhere that badly that night.