A larger T/B will allow the engine to produce more HP , porting the heads would gain you some as well along with better guides is always a upgrade there as well. Maybe swap to the 600 cam and 58E at the same time ?? I know many say go 124 .. but the facts are when you start over laying the graphs you see where the 113 builds out there vs say the 124 HC engines you get a much better picture.
I have a 124 in my own bike that runs extremely well however it does not make as much tq down low as the 113 builds do. So from roll on comparing the two builds the 113 make more down low on avg than the 124 does. However there is a point where the 124 pulls flat out and away.. Now compare the two bikes from a dig then yes the 124 being spun up to 6200 on the shifts will be the winner..
Then in gets into the custom building or modding of the crate 124 and now that only increase's the cost and most still never make more power down low.. Not talking about some one spewing random numbers lets see the dyno sheet, post it.. as the shape of the curve is everything..
I can over lay many 113 builds along with 124 lc and hc builds , then I can add in 124 hc modded builds and all in all for every day riding roll on power the smaller engine with smaller cam wins if you look at the 2200-3500 range for roll on power, spool it up over 4500 and the larger cam bigger CI makes more HP..
The 124 LC engines as a pure crate bolt in 125/135 the 124 HC engine 136-140 hp tq 133-138 modded 124
but increase comp ratio, 2.02 intake some porting should go 140-145 tq 135-140 .
in the end where do you want the power, do not forget about fuel, heat .. in the end you can lean on it and build a very impressive dyno sheet but in the real world that engine is going to be less friendly than the lower compression build.
How much do you want to spend is the real question..