Re: can i put 156 seats into a 146 model
I think the front seats will go in fairly easily, may just have to swap the runners, its the rear where you have problems as they are split folding on the 146 and fixed on the 156. I guess someone somewhere has done it, but I bet they used two rear 156 seats, had to cut the leather to fit around one side of the 146 seats, re-stitch etc etc so its a lot of hassle.
And the door cards will look odd as the leather off the 156 is too small for the 146 door card panel so will not fit either.
Good luck if you go for it, and post on here if you do.