What mounts did you use on the block? Judging by the pictures on the first page you have the truck mounts. If that's the case it could be a reason the AC won't clear the hood. The pre Vortec accessory drive mounts the AC on the passenger side(same as the 307) of engine and I'm pretty sure it's at the same height as the vortec. It consists of 2 aluminum brackets very similar to what you already have but the AC and ALT are swapped. I'm not sure exactly what years have the bracket but I know my 91 and 92 chevy trucks had it, I'm fairly certain 93 had it and 94 should as well. 90 I'm not sure of. 89 had a steel bracket.
With all that said until I put my hood on I wasn't sure my ALT would clear with the truck brackets, but it did.
Cool, I'll look for these next visit to pull-a-part