Harmonic balancer size on 4.3L carb engine
 

I am planing to do some work on my distributor, new weights and springs and the crane adjustible vacuum advance.
I would like to add a timing tape to my harmonic balancer to allow me to setup the timing but I can't find out what the diameter is on the harmonic balancer.
I have not tried to measure it yet, but I have found a reference on the internet(parts search) that suggest that it is 6 and 1/8 inches.
I can not find a timing tape that is designed for this size harmonic balancer.
This is somewhat complicated by the fact that my engine was replaced in 92 with a GM long block and I remember the mechanic that did the install said the engine had been upgraded to roller cam. I am not sure if the harmonic balancer is the same as the original engine.
Anyone have experience with this engine that can make some suggestions?
Thanks in advance.

I believe it's the same as the 6.75" damper found on SB V8's.