60 mm TB is a standard TB with the low bump milled down, you can do it at any mill shop for $10 to $20 bucks. The 62 mm TB is another thing is a full bored TB with a new plate, I bought mine for $115 at e-bay. Check Go-jeep web site for a do it yourseft 60mm TB.
i actually bored mine to exactly 61.379mm at work then made a butterfly to fit exactly, total cost 0$ awesome deal!!!!! u can in fact mill it down to 60mm EXACTLY and still keep the stock butterfly.