Thanks to all for sharing your perspectives.
My decision is to replace the vehicle. Primary reasons: want to be ready to grow; want more payload; want a bit longer wheelbase (this one is 109"); don't really want to fool with the vehicle's design.
Top contenders right now: 2010 or 2011 Ford Expedition; same vintage F-150 with Super Crew Cab and short bed.
Found I can get about $20K for trade-in on the 4Runner, which is paid for, and can get into one of these vehicles with little or no out-of-pocket. Aside from Toyota I've come to really respect Fords, especially the truck end of things.
-Speak