You have 8 pounds of Clays? Why, it's the perfect powder for the 45!
The 45 auto is really an easy cartridge to load for - about any shotgun powder will work fine.
I use mostly 200 wadcutters in mine, but if 185's are on sale, I'll use those.
I'd do as Adam suggests - try some at 4.0 grains, then some at 4.2 before going to 4.4.
Gauging pressure in a 45 is not like looking for pressure signs in a rifle. The biggest indicator of high pressure is violent ejection. With the standard 18 pound spring in the gun, if the fired cases are getting flung 10 feet, you're load is probably too hot.
BTW, my 45 gets fed from a Rockchucker - load in the winter when it's too cold to be outside.