could someone with more experience than I tell if this is a long bed or a short bed frame? I don't know enough about cross members to count and know (if that is even how you would tell)
would like to drop my lwb uni on it and get my 5lugs back and a running engine
That looks like a short bed frame to me. To make sure, check the wheel base by measuring center to center of the axles and comparing to the short bed specs. The further back outboard frame mounts are for the back of the cab, you can also measure the frame back from there a long bed frame will be close to 8'.
Gregg if you want a short uni chassis hook up your trailer and come down and get one . What you need a Long uni Chassis Ok got ya covered there as well you just need a longer trailer both are F100 chassis with 5 luggs .
That is a nice offer. My uni has GM front and rears, which is fine with me but it's now 8lugs, and I'm putting time and money into it so part of me says do it right while the other part says, who's gonna care if it drives and stops.