After visiting both wrecks many times, I can offer the following:
10 Fathom Wreck - A typical coastal freighter built somewhere between 1890 and 1920. Powered by a single boiler (mostly gone) and a single four cylinder quadruple expansion steam engine. She had a rounded bow and wide beam, as she was built for carrying capacity, not for speed.
South Jack Wreck - This was no tramp steamer, this was a thourobred! The SJW fell into a class of vessel known as steam yachts. (Think money, and lots of it!) This is evidenced by her layout, dimensions and what remains of the bow and masts. She was probably built between 1890 and 1910, and she would have been a regular floating palace. She had an extremely narrow beam as noted by the fore and aft twin boiler arangement and the tandem engine assembly (to keep her narrow). The SJW probably sank due to a collision, as she sank very quickly and the engines were still running! (All of the tips of both propellers are bent over!)
In both cases I doubt any serious attempt was made at salvage, because the valuable pieces of machinery--the engines, boilers and propellers--were still on the wreck site.