connecting oxygen lines to converters

I have an 83 TownCar that I recently replaced the entire exhaust system. The replacement catalyc (sp?) converters have a 1/2 inch oxygen intake lines, where the original converters have 1 inch lines. Does anyone know how I can convert my 1 inch aluminum line that travels to the converters to 1/2 so that I can weld it (well, not weld since I an working with aluminum) it to the converters?

Also, would I experience a throttling problem if I do not have these lines hooked up to the converters? I have driven the car around the block, and I cannot get the car to accelerate without sputtering.

Regards,
83lincolnlimo