I see from the link Darrin supplied he is using the Extra I/O plug to (I think) route signals to the new chips no doubt a couple of address lines. That is Soldering FAR IN ADVANCE of my own.
[edit] actually, that could VERY WELL be it.
From memory, the 68882 occupied *A LOT* of the same signals that the 68xxx occupied, You just had to select the specific address lines that the chip used. I do not know the pin outs of the chip, it looks like one pin may be bent up, and wire'd, maybe a "CS" (Chip Select) line, with the rest coexisting signals that both chips use ?
[edit2] Yeah, if that is indeed pin 6 in the picture, that is CE (Chip, Enable input). You just disable that pin on the FPGA, the Existing chips will NEVER receive CE, and it will ignore EVERYTHING ELSE (or how i understand it).