A few years ago I installed a Schweizer hook on my 1953 cessna 180.
The current owner is Ken Sorenson and he may be able to get you a copy
of the 337 I filed.

At the risk of starting a debate, I would suggest sticking to the Tost
hook idea if you are going to do a lot of towing of pilots of varying
skills and currency. It is possible to put too much pressure on a
Schweizer hook if the glider is out of position such that the tow
pilot cannot release the glider. A number of tow pilots have perished
this way over the years.

The tost release will work with the glider in any position.

I used a Schweizer hook because it was significantly cheaper and I
only towed highly experienced pilots and then only ocassionaly.