M37outlaw:
There are lots of routes to go in your quest for more mileage and reliability, mostly depending on your wallet and how deep you want to get into it.
Baseline your engine to see where it is at. Compression test, cylinder leak back, oil pressure when hot, lots of things to consider.
You can perform a rebuild of your engine with an over bore of the cylinders.
There are several engines that will bolt up with some radiator location mods. The Canadian 251, or 265 come to mind.
These engines are considered 25" long, as apposed to the 23" 230 US engine.
Some on this site have changed out the Carburetor with good results for drivability and gas mileage.
Remember these vehicles came with 5.83 gearing, and do not like going much over 45mph, 3000 rpm.
Let us know what you find on your engine.