there are a few ways of doing this. You might have to ask lukenzen or limbo to see what they did with there old D series turbo setups. Some keep the stock compression and run 8psi fine with it. The advantages of lowering the compression is that you will loose a little power on the stock motor but gain alot on being able to put more boost in the motor. I dont think the stock D series rods can handle over 11psi even if you lower the compression.
Lowering the compression can be done the proper way by buying new low comp pistons, they come in may different compression ratios to suit what setup you want. Mine are 9:1 my stock motor is 10.4:1 i believe. So this allows me to boost it quit a bit.
You can also lower you compression the make it do way by buying an extremely thick head gasket basically bringing the gap between the head and the block apart thus creating more air in the chamber between the piston and the top of the head = less compression. Im not to sure how much you loose on it but i wouldnt say it wouldnt be more than .5
Lowering your compression also causes less torque/power before boost comes on so streetablity slowely goes out the window. I dont find it to bad but some people have 8:1 comp ratio. That why alot of guys on here buy B series motors and keep the stock high comp ratio and boost it as much as they can on the stock setup. Thus giving them there stock NA power + boost.
I had it like that once apon a time ago and its much nicer to drive as a daily street car.