I have a 72 chevelle with 355 10 to 1 compression, ported polished, holley 650 double pumper, lunati .515 cam, double hump heads, 2.02 valves, roller rockers, headers, edelbrock victor jr., flowmasters with 350 and 3500 stall, with the 8.5 10 bolt with 3.08 gears, i want to upgrade to a 12 bolt posi with 3.73 gears, i want to know what kind of performance gains i would get, first gear now is violent it will put you in the seat, second is seems weaker, and so does third, can i expect for the higher gears to make the car pull through all gears?

After the gear change you will notice the rear tires will go up in smoke in low gear and you will pull much better thru the upper gears. Also engine braking on decel will be more evident.