what heads?
#21
6.1 heads have a BIGGER intake port since the 6.1 intake is bigger,(try sticking a 6.1 intake on 5.7 heads) other than that they raise compression, Also 6.1 heads have different length vavles than our 5.7s thats why we upgrade to 6.1 exhaust springs only do to install heights on the 6.1 intake spring.