In case this isn't on the site somewhere, if you are using the Speedway 12 circuit wiring harness 91064017 don't use the heavy duty turn signal switch 91062860 with the big red knob hazard pull out switch. Use the basic turn signal switch 91062850 that will work with the two prong flashers on the 4017 harness. Heavy duty switch needs three prong flashers . . . . Wiring instructions have recently been updated but doesn't include this information.
You shouldn't have an issue with it as both the turn flasher and 4 way flasher use pigtail sockets rather than having the sockets built into the fuse block. 12-Circuit Mini-Fuse Universal Hot Rod Wiring Harness Kit (speedwaymotors.com) It will take a bit of this wire goes here and that wire goes there but by studying both diagrams that should be easy to figure out, The turn signal wiring being here 910-62860:Layout 1 (speedwaymotors.com) You should have to run one extra wire to the flasher but that is it.