spools are a bad idea on the street. do a search on the subject, it has been discussed extensively.
what you have is a 7.5 inch 10 bolt. these axles aren't known for their strength but with less than 300 foot pounds of torque and a nice driver they will live for a good long time on the street.
as stated earlier you want a "posi" or positive traction rear end. you can buy various units from jegs or summit including "lockers" that lock and unlock by themselves as you go around turns, noisy but effective. and install them in your axle
or you can do some hunting in a junk yard for one. your going to need a rear end from either a Monte Carlo, regal, grand am, cutlass or grand national maybe some other full size Chevy's of that era. look for the grand national, some came with the 8.5 ten bolt, a much better axle. good luck though, they are like a needle in a hay stack. the monte carlo doesn't lend its self well to adapting strong axles at 57 3/4 inches wide its narrower then most, and the brackets are complicated.
to determine if an axle is a "posi" look for a tag hanging on the differential cover that says something like "use only limited slip gear lube". this tag is often gone so, to be sure lift the rear tires of the vehicle off the ground and with the transmission in park or the yolk held from turning spin one tire. if the other tire spins the same direction its a posi, if it spins the opposite direction its open.