The Mac IIFX used a 64-pin SIMM for its main memory (1MB DRAM was
Apple part #661-0548). 28-pin socketed ROM chips (not modules) for the Mac II (original, 1986 model)
were #661-0639, -0640, -0641, -0642 if the model had the high density
floppy disks, and #342-0639...if the model had the (original) double-sided
Other models (IIx, IIcx, IIci, ...
Here is what you likely need. However, note that I don't own a Mac II and I therefore can't be quite definitive. But I had a thorough look at Mac ROM SIMM photographs on the internet and it seems consistent. Unless they used some specific custom-manufactured connector that looks similar to the standard without being the standard, this should be it (just ...