[cheepin]

I would convert the 203 to part time and put some lock out hubs up front. I bet you gain a couple mpgs there. Also not a bad idea to install an aftermarket air fuel gauge. This will tell you your mixture while driving. Ideal for mileage would be around 14-1.
Timing I like to run 12degrees at idle.
Since the rear has non stock gearing I would check the speedo to a gps. It's probably off a touch. And city driving will never get very good mileage. It's all stop and go, no good for mileage.