Per the recipe in the book
Hook: Mustad 9671 size 6-8
Thread: Black - heavy size "c" - .008
Under body: yellow chenille or wool
Over body: natural deer body hair
Rib: heavy black tying thread (criss-crossed)
Hackle: grizzly - tied full but not dry fly style
(size "c" thread is probably no longer available, so use whatever thread you like)
Deer hair back and tail are an integral unit. Tie in the hair at forward body termination as for wing and then tie down to bend with open spirals of heavy black tying thread.
Take 3-4 turns of thread at tail to secure and cause the tail hair to flare. Return the thread to shoulder in criss-crossing pattern with previous winds. Give turns of thread at tail several coats of lacquer.
History (from the book)
Legend has it that this fly was the creation of an amateur fly tyer in the Bozeman, Montana area and this could well be for it is very popular on the Gallatin river.
Dan Bailey of Livingston, Montana was tying a similar fly as early as 1940, calling it the "Yellow-Bodied Grayback" and still carries it in his current catalog (remember this is in a book from 1972).
There are several similar patterns, such as the Horner Deer Hair, the Goofus Bug and the Humpy. Which is a variation of the other is a moot question, but the fact remains that they are all basically the same and all are excellent.
Most of the above-mentioned deer hair patterns are tied with upright hair wings and in comparatively small sizes as they are essentially dry flies. The "Crazy Goof" on the other hand, is one of the very best flies to use when big hoppers are being blown on the water and is probably at its best when it is used in a large size.
The name of the fly is not at all appropriate as the dressing is extremely sane. The coloration is moderate and the liberal use of deer hair makes it a good floater.
Thats it from the book.
Montana Trout Flies by George F. Grant has a copyright of 1972 so some of the tying threads called out in the book are probably no longer made or hard to acquire. I guess that if one looks hard enough you could find some spool of "nymo" thread.
The heaviest I tie with is 6/0 so that's what I used for the fly in the foto.