There are two styles for seat frames in that folder

My 50 has the one with the cable and pulley .
The other seat frame is off a 51 I think.

Your 53 may not be the same as what I have in my 50?


On the lap belts I made some blocks out of flat bar for the bolts. Gives it a little extra strength. The big round washers came with the kit.

I added a hook to the back of the seat frame from my sons car seat.