I'm assisting with the details of a remodeling of a 1965 Eichler home. The roof is being replaced, the home has its original wiring - is it time to replace all wiring, too? Or will wiring last another 20 years?
while not a licensed opinion, i think you'll be surprised when you open the walls to inspect the wiring. in our 1963, we have 14/2 and 12/2 grounded copper wire... the ground is a bit lighter gauge than modern equivalents, but it's a grounded system and we've seen no reason to change the existing wiring. however, now is the best time to consider additional wiring, we did add 200 amp service (100 amp supply to the original panel plus room for expansion) and ran a few circuits, like 20amp garage circuits for tools and additional runs to the kitchen to handle single appliances like a microwave and dishwasher -- not to mention a 40 amp dedicated run for the mini-split AC/heat system. i'd suggest to look at your overall plan and modify your electric to fit it, giving some room for future adds, too... modern codes require more/dedicated power to the kitchen as well as a few other changes, so be sure to check with the folks-in-the-know here. also look at additional lighting, eichlers are pretty dark -- especially on the exterior... and don't forget cable/telephone/data/audio. we opted to run cable/data to 8 drops in the house and wired it to a central panel which also interfaces easily with a simple home security system -- all for about $500 (self-installed). the foam roof covered it all.