I didn't know that Racing Hart made 1/2" sizes. The C5's were 18x9" 41mm offset and the rear was 18x10" 45mm offset. the 39/44 offset combo will work, if you continue to run a narrow front tire. A 245/275 combo is probably the widest you will be able to run with that setup. I would try to get at least a 9" 41mm offset front wheel and at least a 10" 44mm offset rear wheel.
Later, Steve
Later, Steve