Will the 859 hd unit see the same lake list as my 998 c hd si which has a lakemaster midsouth state card in it? also, will the 859 be able to see the side imaging and down imaging from the si transducer on the 998?

No sir, you will have to have two different lake master cards for those units.

Ok, what about the si and di showing up if I link them together? I read in some other threads on other websites that it would work.

The si/di can be shared if the units have the appropriate updates. Not sure which is the minimum update, but if you update each unit to the latest software they will share

Ten four thanks for the help brothers!