Tom, you had posted when I was typing. The only Syracuse catalogs I have are reprints from 1884, 1888 and 1889. In there it lists the different frame sizes and weights:
Medium frame 12 gauge with 30" and 32" barrels
Heavy frame 12 gauge with 30" and 32" barrels
Extra Heavy 12 gauge with 30" and 32" barrels

The same for 10 gauge.

An 1892 Hunter Arms Catalog (reprint( also lists the same options at to weights, but this disappeared not long after.

I had talked to Buck at your recommendation when I was looking for Syracuse L. C. Smiths, frame weights and he had written down the guns with these weights but at the time he had not seen a Extra Heavy weight gun, that was years ago.

I also have records of 6-8 gauge Syracuse guns, 2 are hammer guns pre 1884 and of the other 4, 3 were owned by a now deceased L.C. Smith Life Member. Of those 3, 2 are consecutively numbered 16463, 16464.As like you stated, there was no mention in any of the catalogs of a 8 gauge guns.