If it is 1890s it has floor joists, not trusses.
Balloon framed houses I worked on had a 1x4 let into the wall studs to support the second floor joists. Second floor joists rested on the 1x4 ledger and were nailed through their sides into wall studs. Your spacing will make some new trusses fall between studs. In that case, the vertical load on the ledger will be more critical than if next to a stud.
I could make suggestions, but you really need a design professional like a licensed engineer involved with this one. It becomes more intense if the second floor has a bearing wall.
Put fire stop blocking in the stud bays or a fire can go through it faster than Grant through Richmond.
Balloon framed houses I worked on had a 1x4 let into the wall studs to support the second floor joists. Second floor joists rested on the 1x4 ledger and were nailed through their sides into wall studs. Your spacing will make some new trusses fall between studs. In that case, the vertical load on the ledger will be more critical than if next to a stud.
I could make suggestions, but you really need a design professional like a licensed engineer involved with this one. It becomes more intense if the second floor has a bearing wall.
Put fire stop blocking in the stud bays or a fire can go through it faster than Grant through Richmond.