Flint, sorry to hear about your father passing. But I'm sure he was proud of the old Colt and would want you to keep it as is. No doubt he knew better than mess with something with collector value and likely bought the Bushy to tinker with.
You can have lots of fun with both. There's nothing quite like an old M16A1 style AR and you'd hate yourself later if you screwed it up.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek