Actually the Collins designed R-388/51J series of receivers was a
predecessor design to the Collins designed R390A. See:
http://www.r-390a.net/
I had a 51J-3 & sold it because it was not in the same league as my
R390A. IMHO, my HRO's, Hammarlund Super Pro & Drakes all outperformed
the 51J by considerable margins.
The 51J is a good looking radio though. But IMO the performance doesn't
live up to the looks & the mistique.
After all this, I have to vote for the R-388 / 51J. No product
detector, but a really nice radio
With a real radio dial 
Take care,
Dale