Well you got 16,18 and 20. All of them. In the FLHR you got 6 pin deutsch connectors to both the left and right hand controls. These are most likely 18 gauge though the print does not say. To extend them you will need to open the deutsch connectors - one is gray and one is black for left and right. You will need to splice into the side going to the handlebar controls from the connectors using Packard sealed butt splice connectors. The red ones are for gauges 18-20 so use those. Because the wires are adjacent the splice should be staggered so that the sealed but splice connectors are not bunched together where they go up your handle bars. You could probably splice in extra wire with two splices but best is to have one splice per wire and go right to the pin terminal in the deutsch 6 pin connectors.
I used 16 gauge on all the wires as that was what I was told and could not find anything listed in either manual. No wonder some of those were tough to peel back the wire with my wire "cutters". It is done, do you think I will have any trouble? TIA, Mark
Tsuter gave you one option. Personally I prefer to add the extra wire at the end. Remove each wire from the connector, cut it at the pin or socket, whichever is appropriate, solder the extra piece onto the end with shrink wrap over it, install a new pin or socket (get from the dealer) and re-insert into the connector. If the solder job is done neatly, there is hardly any extra bulge at all where the joint is. I just think it makes a better installation but that's my opinion.