Not going to happen, the LC was not designed to add a PMMU. The original II was the only one that would.

The options are....

a. get an LCII with a network card and an FPU slot;

b. get an LCIII which already has the FPU slot on the motherboard; and

c. best of all, get a Quadra 605/LC475 and swap the 68040LC for a full 68040.