Hi.
I don't understand the issue with the blinkers, unless you want them to work along with the exixting ones...
...or do you simply want to replace the ones you have with a new set?
In the latter case, just unbold the old, unplug the wires and plug in the new cables, bolt on the blinkers and you're done!
As for the bar end mirrors, if the bolts are too long measure
how much too long they are, and buy two new bolts which will use the same nut, and are shorter by the amount you need.
Shouldn't be a big deal !