I have an Armstrong Ultra 80 Furnace with a Beckett AFG Series Burner. The oil supply tube is stripped and I cannot find the replacement part. The air tube combo. part number is AF50YB (5 1/2in air tube). I have found a similar part number AF65XN but it it 6 5/8in) air tube. Can I use a longer air tube in this Furnace? Will I need to make any alterations to get it to work properly?