8 3/4 chunk question

741 will be fine, although you will be somewhat limited in gear choice. To see if it a "suregrip", posi is for chebbies, raise both rear wheels of the ground and turn one tire if the other side rotates in the same direction it is a suregrip, if it rotates in the opposite direction it is open. To check your ratio, put a mark on the tire at the bottom and lay something on the ground to line up with the mark. Put another mark on the drive shaft. Count the revolutions of the drive shaft to "one" revolution of the tire. 1 revolution of the axle and 2 3/4 revolutions of the shaft would suggest 2.76 to 1 ratio. I'm betting that's what it is.

You can also look for a tag on the rear, there might be one on one of the bolts around the pig that will tell you what the ratio is.