if you were to turbo the engine i wouldn waste time in programming the original ecu, it wont be able to cope under decent amounts of boost. you can buy decent aftermarket stuff, emerald, mbe etc that are more than up to the job. mate has an mbe with a 6bar map sensor in, thats gonna handle any amount of boost you could throw at it.
the main thing with turbo's is fuel - air. if you aint getting decent fuel presure youre gonna melt pistons. i did a 2liter 16v turbo engine conversion into my nova earlier this year and stupidly left the 1600gsi fuel pump on, melted 3 pistons.
as for compression, you can buy pistons for the job, have the std ones machined down or just use 2 head gaskets with a steel plate in between. a fair few companies use that method belive it or not.
if it was to be done properly it would cost about 1500 to 2k for a good job that will last long. i dont think the big end bearings need uprated really, just fit new std ones in.
then again, if a 20v turbo engines are cheap as chips, might aswell, theyre pretty damn quick things
