You'll also likely need a new oil pan.
... any of the other stock pans seem to be a no-go.
I've used the Holley pan on a 2nd Gen and it fit well.
... GM now has a new 'Pan Kit'
that is a great fit and priced very nice
Part number is #19212593
GM Direct and Scroggin-Dickey has them - https://sdparts.com/index.php?q=deta...parts/19212593
And remember, besides the "fuel lines" - you'll need a tank pick-up system to allow for suction, vent and return provisions
The amount of electrical connections and functions will depend on the what/where/how you intend to use the OEM system(s) to control and monitor the engine and other components in the new installation.
Stuff like the 'speed sensor' would only be used for shifting the trans 'if'
you use your original speedo vs. also driving the instrumentation of the OEM vehicle ...
The same goes for many other items, depends on your needs and application.
You can always get a full pull-out
engine, trans, harness/relays/connector boxes, and ECM/DCM system and then cut/splice/paste to fit your needs.
Or ... get in touch with one of the many vendors that will supply a custom harness made to fit your needs.