Here are distance results from my first upgrade:
So far I've installed abec seven spool bearings, abec seven single bearing supported levelwind cog, dual bearing supported levelwind, and I upgraded from two pin to six pin centrifugal brakes. Here's the before and after results:
5500 C3 (stock)
1/4 oz. - 30 yards
1/2 oz. - 43 yards
1 oz. - 54 yards
5500 C6 (upgraded)
1/4 oz. - 31 yards
1/2 oz. - 56 yards
1 oz. - 64 yards
So with the bigger weights I added about 10 yards to casting distance.
Casting 1/4 ounce showed no discernible difference. I was getting about 25-28 yards on average both stock and upgraded. Also, 1/4 oz. is difficult to cast full bore without backlashing, and even more so with the fancy bearings installed! When casting 1/4 oz. after the upgrade I have to engage all six brake pins to keep from backlashing, and even then I need to use more thumb than I do with a modern low pro reel.
The heavier weights cast quite comfortably with 2 brakes engaged, however, and after the upgrades I don't think I could get much further with my new casters.
Now I'm wishing I had tested 3/8 oz. before and after the upgrades....
My only regret is that I installed the single bearing supported cog rather than the dual bearing. The single bearing cog spins no differently than the original cog. I'm gonna order the dual bearing from Mike's reel repair, so in about 11 years once I receive the part I'll be able to tell you if it made a difference.