what is the best compression ratio for a turbo eb falcon runing a GT40 turbo

As it is std at 8.8 unless its a XR6?? Or had head machined ....

unless its a 3.9l eb it will have 9.2:1, xr6's were 9.6:1 from memory...

i would recommend low 8's, ive set mine up at 8.4:1 and looking to run 15-18psi and make 320rwkw

An EB with Crow cam 2222519 can run up to 18 Lb @ 280 rwkw Low 11 second 1/4's..
Spark at this boost is 8* advance though...
With 8.8 compression...There's plenty of std engines runing boost with std compression..Its more to do with TUNE!!
Personally up to 20 Lb is o/k with 8.8 but at that level I'd prefere 8.5 /8.2 with more advance..But it depends what power you are after?? For street 8.8 and 12 Lb would awsome..With this compression there's power and engine responce under boost...
To give you an idea what compression can do my V8 is 7.9 compression advance can go as high as 45* but on max torque curve on 18 Lb boost timing is 22* while fuel ratio is 11.5....There are other variables to consider like some cams bleed off some compression etc...Generally the 6 is more tollerant to detonation than V8's bigger bore...The smaller flame travel helps...

Thanks guys you have been a great help.