building an old school setup for a restored lancer boxtype and was looking for some suggestions from the experts

have a few components already, so was hoping for some input on the missing ones

Headunit: Pioneer KEH-P3700 (used) or Rockford Fosgate RFX-8030 (new old stock) - both cassette players

The display works perfectly for the Pioneer, but no sound comes out when a test speaker was connected. Didn't get to play around with the settings yet when I tested, so it's possible it's still working. I preferred to use the Pioneer (to bring back memories of the KEH-P8250 I had before), but the RF head unit does have more features and looks even more old school

Additional source: Sony Discman D-142CK Megabass (used) + original Sony Plate Arm/Gooseneck (new old stock)
4-ch amp: Rockford Fosgate R400-4D
Mono amp: Rockford Fosgate R500X1D

Still missing:
Rear: Deciding between 2 pairs of JBL GTO 939's or Infinity Kappa 693.11I, unless there are other suggestions for the same (or lower) price points? Would've wanted to find old JBL T545's or T595's, but looks tough to find (or too expensive)
Front: Decided not to install fronts as I don't want to mess with the newly reupholstered sidings
Sub: Was looking at either a single JL Audio 12W3v3-4 or Kicker Solobaric S12L7
Expecting to have the doors and trunk lid treated as well (knowing the boxtype, will definitely vibrate)

The car will only be used at most a few times a month, so really just a toy, but I do want that oomph. Appreciate any input, particularly on the rears and the sub.

Thank you!