Sometimes they show up private sale for $80 or $90 but not that often.
Based on the many questions rattling in your head & the analytical way you look at things, you may need them.
I guess it depaends on how much you intend to do? If your going in deep, I'd bite the bullet & buy them.
Its always easier to get an answer here, but then you have to read between the lines
96BBB 28K 3.42 Bolt-ons
95BBB 100K 3.73 383 New DD...already
fixt the 4L60E twice
95 Black WB4 Hole...ee...grail
96 Black WB4 No holes in this
95BBB 189K 3.08 Old DD