I also have a spesso group N head gasket, I really do not think there will be a problem, as its not just the 155 Q4, also, Lancias and Fiat Coupes155-tbo said:Hello!
I find one article on the net : metal Spesso A group gasket also 12 mm bolts were used to tighten head
If I should change the head gasket, I will use Spesso. Because it is the best gasket for this car. I don`t know do they have that kind of 12 mm bolts in Spesso, but you could ask from them.
I hope this help...