Converting a 103 to a 110 requires complete disassembly of the engine and machining of the cases for the spigots of the larger cylinders. So this is one of those Harley "upgrades" that isn't just a simple bolt on deal. If you tear it completely down, inspect and replace any questionable parts, machine the cases, install the 110 specific new parts, etc., you will have several thousand dollars invested. Before I would go that route I think I'd price the complete job (if you have many miles on the engine assume you will find other parts that need updating/replacing) and then compare to the cost of just replacing your engine with a crate engine like a 124 from S&S or the 120R from Harley. If the 103 is in good condition you could sell it to defray the total cost of the upgrade.
Just a thought.
Jerry