[dirty hands]

well mine was the 1984 2 litre 3 speed auto gl with air con carby leaded
no power steering standard tyres no modifications

its true the car will run on unleaded but not very well in my case
made a trip from brisbane to melbourne - not good on unleaded for mileage

you will find over time the valve stems might wear and you will need to
recondition the head if you are not using the leaded suppliment

what I found was I needed more acceleration and after doing fuel consumption figures I found it was costing me more to use unleaded than when super was availiable
the car certainly lost more than 10 percent power loss on unleaded
no matter what settings I used
head was done up carby rebuilt new timing belt
adjusted timing during that testing period and no better

see what you come back with ?