I would be looking to replace it. It won’t be much fun having a 20-25 year old van when retired and replacing the engine, transmission, exhaust, and then start to get frame and boddy rust to boot.
My vote at this point if for a second opinion. Maybe the oil leak is a valve cover gasket and not the head gasket at all.
The gaskets are molded rubber and with age and heat the rubber hardens. This in turn can causes leaks; much like valve cover bolts loosening over time due to the rubber firming up.
@Jtsanders–I stand corrected. Tester mentioned that the lift would fit another E-150. FoDaddy mentioned that the E-15O series ends this year. My apologies to both.