those ball joints can be a real pain we have done a few on express vans at work, we took it off the car and used a press to get them in place. your best option might be try that or take the parts and new joints down to pedders or a suspension place i dont think they charge to much to install that kind of stuff.
I have the OTC version; they are expensive here inn Oz and it's still a difficult job but easier than otherwise and a) the steering knuckle wont fit of the table of my 20 tonne Bathurst hydraulic press b) using a vice as suggested in the Ford factory manual broke my large Dawn vice (OK like me it was old and fatigued but I was fond of it). There are cheaper versions of this tool (e.g. US General versions made in China from Harbor Freight) but I gather they can bend before the ball joint moves see Adjustable Ball Joints. Too see how to do teh job also see Guide To Replacing Balljoints On Ford E150 Econoline Vans .: Articles