Are you looking for tables/beds, or fences? I've not heard about any retro fences - might be a good idea. We've modified several, but usually just "get it close" then clean up with planer/other.

Tables - used to be a fellow that made aftermarket tables for Mak 16", hopefully someone will chime in with his name. Cost about $250, nice units = heavy alum plate. Had not gotten into the new Mak 16" (blue) last I heard.

Mak 16" is a moneymaker in our shop no doubt, we do some ripping with it. Put in a newly sharpened blade and it will go anywhere. We have better luck ripping down the line first with Mak 8-1/4" at full depth, then follow the same line with 16" at full depth. Saw gets warm to touch, if it is "hot" back off, slow down, change blade, something. If you really "push" the saw it will roll and wander, you need to let it go at its pace - back to sharp blade (the real key). We keep a couple sharp blades on wall and don't hesitate to put one on to make some big rips.

Use shims to pry open behind the saw. Draw lines on both sides and cut from both sides to get a good finish cut, or at least check often.