Which carb adaptor?

[plastic-idol]

I'm ordering a clifford adaptor for a 350cfm holley 2300 tomorrow. which adaptor will I need for a stock 66 head?

08-1641 2 3/4" or 08-1640 3 5/8"?

thanks in advance

 

[mustang6]

A stock '66 head/intake should take the smaller 2 3/4" adapter, but just to be sure you should measure the true distance between the two intake studs on the top of the head.