Les,
The main problem with the Dragonfly is that several components were changed during it's short production run - the wheels were included in this. Early Dragonflies had the same hubs as the earlier Mk5 machines - later models (from mid '56) had British Hub wheels, but these were never shown in either the parts books or owners manual.
I assume you have the later hubs - if so, lets assume your rear wheel is assembled correctly and the brake plate does not foul on the drum, fit just the locknut to the brakeplate and offer the wheel up to the swinging arm. With the brake anchor boss touching it's anchor plate, check the distance between the wheel spindle locknut and swinging arm - then fit a spacer of that width between the brakeplate and locknut. You should now be able to tighten that side of the wheel spindle without distorting the brake plate. Moving to the other side of the wheel, there should be a spacer between the bearing lock nut and the inside of the speedo drive, that keeps the speedo drive gear from bearing on the end of the hub. There should then be another locknut for the speedo drive, with maybe a washer to adjust the whole assembly to the same width as the swinging arm. The chain adjusters should then be fitted on the outside of the swinging arm.
Don't hold on to any false hopes regarding the drawings - there are very few that refer to the later Dragonflies and definitely no assembly drawings for the wheels.
Regards,
Eddie.