Will look tomorrow if you need still .
I know on my 440 between a M1 and BG825 with 1"spacer and modman with twin 600s it was a wash HP wise .
BUT . Car slowed in the 60 and lost et , same MPH .
Could not get a good AFR , ran lots of jet/rod etc still showed lean . Even tried 4 hole spacers to improve signal . No help .
Added a full length filler to reduce plenum volume , inconclusive .
Felt great on the street .
May get a chance to try it on my 505 this year . I feel this will work better plus leaving on a 2 step at higher rpm
PS , measured plenum volume was approximately 5 litres
Tex