I'm working on an 82 shovel fxe. I don't have any hardware for the shocks. It looks like the bottom holes are threaded but the top ones are not. Can I just buy some bolts, washers and nuts? If so, what size bolts do I need and what grade strength?

 

you need the proper shock mounts or nothing will line up,
see this as a guide, many others are available on ebay or new from many after market dealers,...
Upper & Lower Rear Shock mount Kit Zinc Harley Shovelhead FL FX FXE 1973-1984 | eBay

 

Swing arm bolt is 1/2" fine thread, you'd have to measure to get the correct length, as Pete said the frame mount is dedicated, can't rig that gotta buy the correct stuff.