Atf for 904/999 transmission

Type F does firm up the shifts. Look on the back of a bottle of B&M Trick Shift. It says something like "Compatible woth Ford Type F", or some such. That's what it is. Where in the world did you get the ATF+4 recommendation?
I can't remember Google i think I wanted to use mopar brand atf and atf4 was what I found that was compatible on the mopar brand