When you say “fuse box kit” what are you specifically needing it for?? Just a few add on circuits?? How many??
Ive used the American Autowire highway 22kit in my 78 Camaro and I forget which one in my 442….but those were complete rewiring jobs
I favor American Autowire personally
https://www.summitracing.com/parts/aww-500383
I would go with a COMPLETE driveline if it works
Ive rebuilt a few GM transmissions and the 4L60e has its weak points but can be rebuilt cheap and easy with upgrades in a weekend……need a very big table tho. Plenty of resources and exploded diagrams and takedown/rebuild videos to teach any newcomer. Never be afraid