I think why they want your carb to install it on as a lot of carbs are different and if they have to make one for the carb they have it there to do it on as the geometry for these throttle plate adapters have to be exactly correct or you run the risk of screwing your transmission up. That what I was told before when I was trying to find one for my Rochester 4 barrel and no one made them for a 69 carb. I have heard of people sending there carbs to them and not having any problems with them returning it. Please post what you do and what the thing looks like if you have it done by them.