I didn't want to admit this.
I used the same brass 90 for a few weeks, before this Z3 came in way back. It had my Duron 750 running about 10C hotter than the Z3 on the exact same cooling system. Point is, it worked...just not great.
I made the hold down from a length of 3x3 alum. angle also from Home Depot. I cut it just wider then the socket, and drilled 3 holes. The center hole was a size larger than the fitting, so it sat on the brass, with the fitting poking through. The hold downs were just 3" bolts with nuts. I shaved enough of the head with a dremel, that I could hook the centre zif lug, without touching the mobo. The bolts poked up through the angle on either side of the fitting, and I hand tightened the nuts. I don't remember exact temps...but it was real close to 50C on a stock 750.