It's a Buick,Ronnie.As to the carrier,Bill,if you want to use ,say a 4.11 or 4.56 gear on a posi unit that came with ,say,3.36's you'd need to either get a posi unit made for the 4 series gears,or you can get a spacer ring that goes between the ring gear and the three series posi unit.Personally ,I've had trouble with the spacers when using Drag Radials or slicks.As to Ms.Bella,since you like to drive her some significant distances,3.70 would be lowest I'd recommend. 4.11's suck on any kind of distance driving at 65-70 mph highway speeds with 25-26 inch tall street tires,as will your fuel mileage.