Wow, that was a long time ago… the 401(k) was in its infancy in 1978. Call Motorola and speak with the H/R Department, benefits coordinator, or plan administrator regarding your plan. Motorola has several plans so you may need to call all of them..
You can also check with the US Department of Labor abandoned plan website http://askebsa.dol.gov/AbandonedPlanSearch/ the National Registry of Unclaimed Retirement Benefits https://www.unclaimedretirementbenefits.com/ You can also check on http://missingmoney.com/
Good luck with your search
Are you looking to find out what the balance of your old 401(k) account is?