Coming at it from a different approach.
Has he got the subframe spacers in? The exhaust is a cunt to fit without them when running a SBC, also check the phasing of the starter.
Mine had to be turned about 90 degrees to fit my headers.
Admittedly mine is a Holden but same principle applies. The passenger side is fucking tight fit for exhaust regardless but more so on the passenger side because of the starter.