Just find a used arm it wont be too expensive somewhere around 250ish. A full length arm will be a lot quieter than the tunnel mount. If you race a lot the tunnel is better but loud. It all depends what your looking to do. Also obviously poly mounts vs rod ends makes a big difference

I'd get one to be on the safe side. I snapped a stocker in half on pavement, on street tires, @ bolt on LT1 power levels tho w/ an M6. not even launching from a stop, was rolling at 5mph and floored it.. had to replace my DS, output shaft seals(think thats what their called anyways) in my T56 and thats when my slow diff leak started as well.