Two things to consider:
1) You will not be able to buy and “restore” a car for $4500. You may be able to tiddy it up, but not restore. Your best bet would be to find one that has already been fixed up. $4500 should get a nice one depending on your location.
2) Classic iron and MPG usually do not go in the same sentence. Carbureted heavy classics or less forgiving then the newer FI models. Driving habits will greatly affect MPG, given the same car one guy may get 15+ MPG while a lead foot may get 8- MPG.
Just my $0.02
, use the advice of others, but in the end get the car that suits you best.