Just had the 350 replaced in my 98 Z71 truck. Crate motor replacement 350. I dumped the oil at 900 miles and it is BLACK BLACK BLACK. The drain plug magnet didn't pickup any shavings and all looks well, but is it normal for oil to be that dark on a fresh motor?

Depends on what they lubed the cam and other things with. When i lubed up my cam and lifters one last time before buttoning up the oil pan, I lubed it with black moly grease and after a 30 minute cam break in and about 150 miles we dumped out the oil and it was already BLACK . I've done two or three more oil changes with regular ole Valvoline dinojuice and it came it out nice and brown at 650, 1500, and 2000 miles. Then i dumped Mobi 1 in it and 500+ miles and about 40 passes down the 1/8, it still looks nice.

I usually change the oil the first time on a fresh engine with 200 miles on it. On the ones I have built, the oil came out black due to the assembly lube I used. All of the subsequent oil changes, it has come out looking nice and clean, the way it should.