Forgot to update... for anyone considering the ZF swap in their F-150, I would highly recommend it.
I had a heck of a time tracking down a ZF5 trans for the truck and a lot of salvage yards kept telling me that it can't be done. Finally found one for a reasonable price two hours away. They assured me that it was an external slave (AlanD later corrected me saying that the external slaves were only for big block bellhousings), and when I got up there, naturally I discovered it was an internal. The yard guy assured me that the ZF used a heavier duty internal slave, so away I went.
So I got a heavy-duty internal slave and put the trans in, only to discover that the hydro line is different, so that had to be swapped out. I also replaced my master cylinder as I had detonated the push rod when the old slave seized. Tried to bleed the system and found that the new hydro line was defective and refused to seal. Got it swapped out and found that the new slave wouldn't function. Replaced that and had a heck of a time getting it bled.
As if that wasn't enough, I also found that the ZF was missing the shifter stub. I also discovered that shifter stubs for them are a bit hard to come by. Ford considers them as obsolete and prices elsewhere are sky high. Finally came across someone on Ebay with some NOS ones for sale and they accepted my offer. Got it only to find that there was a Ford tag with the correct part number but the casting number on the part was not correct for my truck. It fit the transmission but pointed the shifter at the underside of the dash. After help from Holyford86 and examination of a junk E-150, it was determined that the shifter would be correct for an Econoline van. In my case, I had a problem.
After considering my options, I solved the problem in short order one evening by pulling out the concrete tools.... a piece of 5/8" rebar and the rod bender/cutter. After obtaining a shift boot from an early 80's F-150 with a 4-speed, it's all together and working great.