7 1/4 to 8 3/4 Newb Questions

If you haven't already asked the seller about the driveshaft, look in the car to see if it is laying inside. If it isn't, the best thing to do is just measure. One thing to check, is to see if the 8 3/4 has a big or small yoke on the pinion. If it has the big one, and yours is the small one on the driveshaft, you can buy a conversion U joint to make it work.