A lot will depend on how you define "hassle". To me, the easiest is to swap the whole rear axle assembly with another good one of the same type and with the ratio you want. Just changing the gear set (if that's all it needs) would be the next easiest if you have the proper tools and know-how to set them up in your housing. To get a stronger rear end and keep the same wheel bolt pattern, you're looking at getting a complete drum to drum 8 3/4 from a '66-72 Abody, the shock plates, and shortening the driveshaft. Lots of money, but, a great upgrade. It would also be much easier to change the gear ratio or add a sure grip at a future date. Another option is getting an 8 1/4 Complete rear from a '73-6 ABody, shock plates, and also shortening the driveshaft, but, it has the larger 4 1/2" bolt patter for the wheels.
