If you want to build a full detail 956 shorttail without spending the money on a S27 transkit you can make one from a Tamiya 956 and add the rear from a Tamiya 962. It's some work but doable.
You should be able to do that in Jaegermeister colours with existing decals.
There was a decal sheet for the Schiesser car from Blackbox but they are long gone.
If you have to have the Spa car this place might be an alternative:
http://www.scalemodeller.de/A_startp...tpageframe.htm
They do the Schiesser decals in 1:18 with an ALPS printer. It should be possible to print a 1:24 sheet as well. May be a question of the price:-)