I have a 4 bar setup and 4" dropped tube axle on my 39 sedan and I have to say that it handles and rides very well, I am considering the R&P IFS setup to get a front steer setup. I am using a 605 box in my 39 with a SBC and the exhaust cooks the seals in the 605 to where I have to rebuild it every 25K miles or so.
After looking at a few more stock modular exhaust setups I might be able to get away with having a rear steer setup. It would save a ton of money and work if I could go with a 4" dropped axle.
I found some measurements for the 4.6 & 5.4 DOHC engines today and the 4.6 maybe narrow enough for me to juggle it in without butchering the firewall.