I am trying to find the correct replacement wet end but am not finding a match. It's for a Catalina Spa - Waterway "The Boss" High Performance Wet End Pump - 4.5 HP - 2X2 side discharge. There's a few I see that appear to be close but the housing of the wet end looks a little different. Does that matter or will the thru bolts line up anyhow? Any help would be greatly appreciated

Waterway has changed their wet end design over the years.

What you need is probably this now:
http://spapartsnet.com/Pump-Parts/Wet-E ... 4_0_1.html

You'll probably need the 48 frame 2" suction and discharge version. Pay particular attention to the details on that link.

Thanks.