The Crown Victoria suspension from the 2000's is a pretty good fit in the 40's Chev frames. The nice thing is that the level portion of frame where the original knee action crossmember is bolted is in the correct location to accept the Crown Vic. The pluses for the crown Vic are 12" brakes, R&P steering, aluminum crossmember and lower control arms, low cost from junk yards and good service parts availability. The minuses are, It's too wide and needs to be narrowed, 16" minimum wheel diameter, should use deep backspacing (flat outside) wheels. To fit the Chevy, I narrowed mine by 4-5/8" which coincides with mid 90's T-Bird or Mustang R&P and sway bar from a T-Bird. To narrow the crossmember I cut it and made bolted splice plates to rejoin the halves. These are bolted with 1/2" GR-8 bolts and deep nuts with hardened SAE washers. When mounting the crossmember I used the CV anti-crush tubes recovered from the CV. They are easy to cut out of the CV with a hole saw that just fits over the top as they are only welded in at the top of the frame. The lower arm rear pivot bushings were modified to bolt to the existing frame holes for the Chev K member arms which need to be removed or modified. I was making a new trans mount crossmember anyway and mounting the master cylinder to the firewall. I'm also using Moon disks to hide the wheels that don't look right on an old car. I also made a new crossmember from square tube to mount the radiator horse collar. If anyone wants to do this I can provide drawing files to have the splice plates and lower bushing mounts CNC cut.
