honestly wish I could buy everything genuine Toyota.
but, since that doesn't work well for the k5, parts come from everywhere now. AutoZone, gm dealers, wrecking yards, amazon... be careful with chinamazon. i use it a lot, but there are a lot of things marked "genuine gm" that are most definitely NOT. be prepared to return stuff.
Classic industries is a conundrum. they are local to me, and i always think i can pop in and get stuff.. always ends up being a customer service nightmare. Next time I will have an order shipped to my office 15 miles away! they do have a lot of square body stuff though.
-edit- honestly, its kind of down to a case by case basis now... some things you definitely want to buy genuine gm or ac delco, and other things are just as good from autozone. other things are just flat out not available...
anymore, might be best to search good ol CK5 every time you are looking for something, and if nothing definitive pops up, get in the garage or the sub forum of choice and start a thread?
"hey where's the best turn signal switch for blah blah blah..."
'who has the cheapest patch panel that work"...
"why wont these 72 inch tires fit, and what have i done..."
etc.
be prepared for people to tell you to hit that search button if its a common topic.