I have a craftsmen 18.5 hp 42" riding mower and I am changing the blade belt. I have it all back together except for item 61 (the spring ext. electric clutch). I know where to hook the flexible wire end to but I don't know what to hook the spring end to

Which end of the spring is puzzling you? It connects to both the deck and the moveable arm but you need to do this before installing the belt. Remove the belt, install the spring, compress the spring then put the belt on. No free Sears manuals but you can buy them at Parts & Accessories | Shop & Find Lawn & Garden, Appliance Parts at Sears PartsDirect | SearsPartsDirect.com

The hard part of the spring is where I do not know where on the deck to connect to. The other end goes to the sway bar bracket.

Remove the belt, keep the spring attached to the swing arm and hold the spring by the open end. Move that open end near the deck tangent to the arm, perpendicular, and see if it matches a hole in the deck or a small bolt head sticking up.