Hm, UPGRADE is an interesting word, not sure I’d use it here.

If you’re just after looks ok but if you’re into riding, test ride a 2009 CVO Springer (it also has a 240 rear) and don’t handle real well but keep in mind that with its 32 degrees rake (designed for a Springer as they need a steeper angle to work) it’ll handle better than adding a Springer to your Breakout with its 36 degree rake. 

Just as an indication of what I'm working towards, this bike is an inspiration for my build

This is just my two cents worth but I ride a cross bones and a large rear Tyre doesn’t help a springer. Mine came with a 200 rear and a 130 front. Now I rum a 180 and a 120 on the same rims... pirellis. FWD controls for better ground clearance and I can carve up the twisters with the best of them. The SE 110 helps. If you go old school springer you have to go old school Tyre sizes that they were built to use.

This is just my two cents worth but I ride a cross bones and a large rear Tyre doesn’t help a springer. Mine came with a 200 rear and a 130 front. Now I rum a 180 and a 120 on the same rims... pirellis. FWD controls for better ground clearance and I can carve up the twisters with the best of them. The SE 110 helps. If you go old school springer you have to go old school Tyre sizes that they were built to use.

Just as an indication of what I'm working towards, this bike is an inspiration for my build

Spend the money on a 110kit, 89cc heads, 58mm manifold & TB + pushrods, ignition coil, cam & tune. Id also recommend upgrading the front rotor to an over size arlen ness job. Or fit a trask turbo