Head shim for falcon

[smegoal]

Hi just looking for some advice
my cousin was given ct20 from a 2.4lt diesel he piped it up to a Australian ford falcon as a burnout comp car he couldent go more then half throttle or he would kill a auto box. 3 auto boxes and a few diffs later he relised it was too much for the auto, i let him use my 5 sd supra box all better right NO one hour later blowen head gasket warpt block and a crake in the head between the valves. Hes in the process of rebuilding the motor but none of our turbo guries will advise him hom much shim he needs one of his dads mates is willing to cut it for him for free (well for beer any way )
Any advice would help he want to run 10psi - 16psi
this is the spec of the engine
4.1L Alloy Head 6 cyl
Bore and stroke: 93 x 99 mm
Power: 103kW at 3750rpm
Torque: 316Nm at 2400rpm
Compression ratio: 9.35:1