Ahmet:
Let me address a few of these things you propose, from our veiw point.
"A 951 has many improvements from control arms to strut mounts" Who wants aluminum non re-buildable control arms anyway? Strut mounts should be replaced with camber plates.
"Don't forget the 944 turbo would be stressed less with the same amount of power" Totally incorrect, with forgrd pistons at 8.5 to 1 or a lower compression head gasket the stress level would be the same.
Thermal efficency and volumetric efficency are 2 totaly different things. What do engine builders start to do when the volumetric effecency has reached its limit they turn to thermal, buy increasing the compression ratio. The 951 is OUT DATED!!!! in this respect, with modern tunnable ignition systems. The compression ratio of modern forced induction engines are reching the 10 to 1 range.
"it's a different car" Yes it is a different car, with so many simularitys that its not funny!
"It has a stiffer chasis, heavier duty suspension/brakes, transaxle" We address this in our prior post!
"engine block, sodium filled valves, double walled headers etc."
The blocks are the same, with a 951 head they are the same, Double walled headers are just to control heat, build your own cross over pipe larger to improve flow and turbo response time.
"BTW, I bought a 'worn out' 944 turbo for $3150, and it's fast. "
In 6 months to a year from now see how much it costs you fixing all the small problems or a major failure.
Kevin
PCM
www.perfectchoicemotorsports.com