Need some help! My plans have changed for my cutlass I have an olds 403 with 4a heads the entire engine is in the rebuild shop as we speak. Currently yhr heads on the 403 are not smog heads, I want to make them smog heads. Where can I get the inserts that go into the heads for the a.i.r. tube to seal or is there one ??? Another question is I I have a set of 3A smog heads from a 78 olds on the shelf would these heads be a better choice and if so any special requirements. Also have a set of 5A heads. I AM NOT BUILDING A RACE ENGINE JUST ONE WITH A BIT MORE POWER THAN THE 307 CURRENTLY INSTALLED. I know the early 7a heads would be better but they are not on my shelf. Also I must keep the computer for a few more years. Advice Please!