I only know of 1 facelift 156 V6 in the country and thats a white SW owned by Chris155's father! they were never imported into this country in that engine spec.
the pic you link is a btcc touring car and you will probably find it has a highly tuned 2.0 4 cylinder in it and not a V6!
if you want a track car I would have thought a facelift sillyspeed would make a good choice.
V6s will struggle with brakes and high nose weight in corners where the 4 cylinders wont struggle so much with these.
to not consider a GTA is to be frank, daft. if you'd driven one you would know why. a well setup GTA with Q2, FSDs and the 330 brembos would be a leathal weapon on a track.
faily that for the track I would go for a 4 cylinder, on some good springs with drilled/grooved discs and race pads with a load of strut braces and a good harness.
if you went for 159 i would go for the 2.4jtdm. very smooth and 210bhp which isnt that far off the V6 3.2 without the running costs.
1999 156 1.8TS Sport Pack 3
2001 166 3.0 V6 24V Super
2003 156 GTA 3.2 V6 24V
2005 156 1.9 JTDM-Jet Sport
2008 159 1.9 JTDM Lusso
1997 GTV 2.0TS Lusso
2001 147 1.6TS Lusso