The original pattern has a goose biot abdomen. If you apply a layer of Hard As Nails before wrapping, the fly becomes almost indestructible... the one below caught five wild trout to 12" and looks good enough for another dozen.

The original also uses beaver dubbing for the thorax. In the interests of resilience I've used Fly-Rite poly dubbing - this can be dubbed tight and so extends the life of the fly.
Engle's preferred hook is the TMC 101 in #18 to #26. The one below is on a TMC 101 #24, with a thread body replacing the goose biot. It takes a bit of practice to work with an appropriate amount of showshoe at this scale but it worth it. Tails are exaggerated to act as a trigger whilst stabilising the fly as it alights.
There's a simply excellent SBS here.
Tie some up, hit the water - action assured.....