The '96 GTX has 3 engine mounts not 4. If you have to tilt the motor, something is pretty bad off as you can get right to the bolts holding the carbs on by standing on the left side of the ski and leaning over the motor, allen wrench in right hand. Why do you have to tilt the motor?
Ok, just read down and noticed you are having bolt issues...most likely with corrosion buildup. Remove the 3 bolts holding the motor to their mounts, remove the large clamp on the rubber draveshaft boot, remove the 2 bolts holding the front motor mount in place, remove the exhaust headpipe and expansion chamber (leave the manifold on). After you've done this you will be able to slide the motor forward to slide the shaft out of the PTO and rotate the motor to give you easier access to the bolts holding the manifold on. But be very careful as those bolts will lock up too. Doos are very prone to this problem and you may find that allthe bolts on the motor will be very difficult to remove. You can do it, just be very careful. Any problems when you get into it just ask. I'll help out as much as possible. You should see a rubber bumper plug on the driveshaft when you pull it out....don't lose that as you will need to have it in place upon reassmbly.