Maybe I'm way wrong, but I sort of assumed the only Shimano indexing 6-speed was DA until the new 600 SIS came out, and that the DA's freewheel was uniquely DA, but I see he ran the 600 freewheel and it was fine. This after putting 6sp DA indexed on a Cilo, full DA, and having to have the freewheel rebuilt when my relative wore it out. The shop said "DA only" and rebuilt it for $35.00 (REI).

I also assumed there was no Suntour indexing 6-speed, as the early indexing Suntour was 7speed when "they too little, too late(d)" the indexing arena. I do remember restoring an 86 Centurion with Suntour Sprint, and I can't remember if it was indexed or not.

Then again, I exist in a mental fog.