I've owned 550A, B & C models and the grease fittings are the only difference as far as I can tell.
You'll get a lot more "bang for your buck" with some minor disassembly, and drilling some new 5/64" grease holes (which match the existing holes) in some new places. Except for the improved operation, these changes are invisible. Will only take about 20 min.
• Add 2 holes in the bottom yoke. Undo the set screw from the bottom of the ram, and slide the pin out. Carefully mark and center punch the part because the drill bit wants to wander in these locations.

• Add 1 hole half-way down, front center of the ram. Before any drilling starts, pull the ram out though the top while you have that pin removed. (On a 650, this hole is better placed on the RH side.)

Then buy a "needle nozzle" grease gun* (as commonly used on chain saws) and start pumping in generic
chassis lube. (HINT: The
blue and
teal colored greases make less of a mess than the
red or
black greases.
*
Amazon grease gun link Hope this helps.