My overhead garage doors use extension springs. I thought I might
convert to torsion springs and looked on the web for a kit. All I could
find was the springs themselves, and various other parts. No complete
installation package. And I did a LOT of searching - probably 2 hours'
worth.

This is strange - my conclusion is that the installation package comes
with the door (tracks, hinges, rollers, springs, etc) and that's it.
What about if you wanted to build your own door? You'd think that you
could get a kit SOMEWHERE.

It looks like I would have to buy all the parts separately - hoping that
I got ones that went with each other. And, of course, paying a
premium over what a package/kit would cost.

Frustrated and baffled,
Bob