Hi man, saw your thread on 318ti also.
Have you looked into nissan sr20det pistons?
They are forged standard, very strong and many aftermarket options are available, with differing compression ratios and dish cc size off the shelf, at good prices.
They are 86mm bore, 22mm pin diameter, so would couple with the 140mm m42 standard conrod.
The compression height is 32mm, and m42 is(as far as i can gather)31.65mm.
So with a thicker head gasket to lower static compression, these pistons may be a cheap FI application without milling block to suit shorter rods.
These nissans are plentiful in australia,nz, japan and the us but not sure on the silvia's following throughout europe.
Your thoughts?