steve when i fitted a turbo to my 1993 1200 vauxhall engine all i did to bring down the compression of the standard N/A engine was to fit a copper gasket spacer (got a machine shop to cut out a sheet of copper to the same as the head gasket!) use the copper gasket as you would fit a head saver shim! then fit your head gasket and rebuild engine! (So all you need to work out is how thick you need it to be to reduce the compression to the level you require !

Works honest! actually it worked well! alot of people got a fright from my 1200 nova! it had around 90BHP! (Std Engine had 45BHP!)

also this method does not require any mods to your original parts to accomplish!! apart from the equivelent of doing a head gasket!!