I've been fooling around with various ideas for building a more "modern" suspension set-up for my T-bird for quite awhile. These are some adapters I designed for the purpose of putting '65 Dodge screw-in upper joints on the 55/56 A-arms. These are a straight bolt in (and the taper pin fits the Ford spindle correctly) - but they cost a bit to make unless you can machine your own. The steel ring is an internally threaded "builder's aid" sold by Speedway for guys (dirt track racers) that like to weld up their own A-arms. The screw-in uppers are also really popular with the people who build custom arms for the Mustang II front ends. These ball joints can be had for about $15 and the rings are $7-$8 each. 
Unfortunately I haven't tried building the lowers yet - but it certainly looks like there is room to construct a bolt in part for that application. I believe there are screw-in (or press-in) lower joints with the proper pin size for that position too.
The other idea I've been looking at, is to build a replacement upper pivot shaft that incorporates a little more suspension science than was designed-in circa 1955. The Mustang II systems have 3° "anti-dive" for braking stability and it would be a worthwhile improvement for the T-bird. A slight forward shift of the attachment holes would net a bit more caster which I believe would be helpful to highway stability.