I've found the LED clusters are too big to fit in the light housing. My old Perko lights just weren't big enough to get in a lamp large/bright enough so I replaced the entire set of lights. Picked mine up from Australia
from e-Bay and they weren't that expensive, about $45 IIRC. I also picked up a complete set of series 25 LED lights
off of e-Bay for $66 normal retail over $150. The only drawback with the new LED's was the footprint of the new light wasn't big enough to cover the footprint of the old lights so I've got a couple of exposed mounting screws.
We came in last night about 20:00 hrs and I must say they are "Bright"!
Sorry 'bout the poor quality pic.