How do you fix SWB seat recliner mechanisms to hold up better?
 

My 66's seats recline on the passenger side when there is a heavier person in it. What do I do to make the rachet mechanism work better.

Take it apart, clean it thoroughly, check to see if the spring mechanism is firmly in place and if the reckiner gears are lining up properly. If it's all bad, you have two choices, weld it into a fixed position and live with it, or buy a crap seat with a good recliner mechanism cheap and gut the recliner parts you need.

Well I've taken it apart, and it seems like its the springs that are too weak. I also replaced the brackets once and the replacements were junk. I don't think the spring is replaceable is it?

Are you talking about the coil? If it's shot, than your best bet is to buy another reckiner and gut the parts.

I am talking about the spring that holds the two gears together that do the actually holding up of the back rest.

Even if I gutted another one, I would have old parts, is there anyway to get new parts?