When I took my engine out, I noticed that the PS pump could be locked down or pivoted indicating that, with the AC compressor not installed, you can adjust the belt tension with the PS pump.
I think that the locking bolt is under the pump and accessable through the round holes in the pump's pulley.
Whatever the case, take a good look at the way the PS pump is mounted and you'll discover how to set it so it'll take the slack out of the belt.
Hope this helps!