If you don't plan on fixing the 4wd, then I'd say go for it. With these tires being shorter than the turfs, it will tend to bind up the 4wd. The axles are geared for a specific ratio of front-rear tire height. If you left turfs on the front, you might be alright though because they should be able to slip unless you're on pavement.
Regardless of the tires, the 750 is a narrow tractor. If it has a loader, i wouldn't want to drive up or down a steep slope with a load in the bucket. Also, I would never drive this tractor across a slope. It's just too narrow. What the ag tires do allow me to do is go comfortably up or down a slope with a bush hog on the tractor without being scared of skidding down the hill. Would I want to go up and down slopes all day long with this setup? No. But for cutting the trail down to the bottom at our farm, cutting my shooting range, and pulling a small disc for food plots, it does just fine.
What do you use the tractor for?