Two quick ??s: plug holes, replace floor joist

It seems that expanding foam is the recommended way to plug small holes.. I have a garage used for misc storage that I'm thinking of rehabbing. Generally sound, but there are places around the lower sill where daylight shows through, ditto for along the roofline. Along lower sill I though laying in screen (to keep rodents, bugs out) then fiberglass batts, with vapor barrier over and sealed in w/drywall. Holes are really gaps, anywhere from 1/8 to 1/2 - 3/4 inch.
I don't see much info on replacing flooring joists, feel free to point me in the right direction (yep, tried google already). House is 1900s farmhouse, not historical material. Some joists have ?dryrot? seem pretty punky. Joists have wiring through them. I thought I had seen at one time a tv show that used engineered joists as replacements, complete with holes for wiring, danged if I remember details or can even figure how this might be done. Guess the wiring would have to be pulled first, then re-wired. How else to sister/replace a floor joist with wiring/holes for plumbing in them?
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