I did two mods where we replaced hd-85 harmonic operators on tac20s with movfr's. We retained the TK clutch and doors on that job. Instead of a connecting link from the end of the drive arm to the clutch we ordered connecting links with a bracket on the end with slots for two bolts. Took a roughly 18x24 inch piece of 11 gauge sheet steel and a ton of self tappers with lock washers and loctite to secure that plate to the raise ribs on the car door and bolted the connecting link to it. It's been years and no issues.
Honestly tks clutches are not bad. The nice thing with a tk clutch is it doesn't rely on the connecting links angle to retract the vane on the clutch, meaning the drive arm doesn't have to actually connect to the clutch itself . If your going to go through all the trouble to replace the clutch I'd be thinking of new cab/hatch doors made for GAL clutch/pickup rollers. There's really no gain in going to a gal clutch if keeping the tk doors, they're made so differently, then you have to Jerry rig the pickup rollers onto the tk hatch doors, and possibly create issues with the depth of clutch and pickup rollers not working out. I'd just buy a new tk clutch and replace it so it's new as well, as a part of the mod.
I have one job on my route where my company (long before i came here) did exactly what your saying, they put a gal clutch and pickup rollers on tac 20 doors. It was a hack job. It's a pita to open a door, the bar from pickup rollers to hook bill is too far away from hole in the door, you need a three section extra long drop key.
Having seen it done both ways, my vote is on a gal operator and tk clutch. It's just a much cleaner and in my opinion better option.
We also have used the MOVFR on past TK/Dover mods, the nice thing about reusing the clutch and the pivot arm is you can raise the operator up to clear any car top obstruction, and just move the connection point.
Goat: Who did you talk to at Smartrise about the interface board to the TK LD-03? I've been told know by both sales and tech support. They use IPC door boards, which don't work with 20VDC according to IPC. I'd love to go this route thought.