transmission.

[Donut]

84chvy, call around, it may be cheaper in your neck of the woods.  That said the builder will want you to install a new torque converter and more than likely an aftermarket trans. cooler.  (IMO both good ideas)

Some shops can cut a couple hundred off of the rebuild cost if you R&R yourself.  Talk to the builder.

My '73 got a "crate" transmission as I didn't have the time to attempt it myself.  The '86, I'm attempting, as I got time and no $.