Original dash harness Question

[cgster]

I originally was going to go back with an old school 350 engine but decided I may go the LS Swap route with my 67 C10 If I can get a better handle on what all is involved.
I had originally purchased a new (original style) Underdash harness and fuse box from American Autowire as well as some original under the hood/lights wiring harnesses.
I know very little about wiring. Can I still use these original style harnesses if I end up doing an LS Swap? Thanks.