After a long night i found out that there is difference between 2.0 and 2.3 pistons and presumably i would lost some CR? But how much? Maybe a thinner t7 head gasket will do?
I also found a camshaft chart so now i know whats what.
There is a similar thread on uksaabs.co.uk but strangely this site looks dead.

 

For now is the inside of both engines not so interesting, let's begin with the ignition:
Do both the engines have a DIC or has the B204x "old fashion" ignition (with a rotor inside it) at the end of the cilinderhead?

 

Both engines have red cassettes and cylinder heads have the same part numbers

 

Because it isn't known about the MY the SAAB9000 of @filipt5r is, i have selected photo's of MY1990 and MY1996 and of each ModelYear a picture of the version with the B204x and the B234x engines.
Look at the cilinderhead, such as the ignition i earlier menitoned about, but look also the intake manifolds and other parts in the engine rooms and indead, the situation of both engine versions in the MY1996 are more closer to each other as in those of the MY1990, that is as true at it could be.

MY1990 2.0-16

(This one hasn't an airco, for now not important)

MY1990 2.3-16

(This one has an airco, for now not important)

MY1996 2.0-16

(This one has an airco, for now not important)

MY1996 2.3-16

(This one has an airco and a LPG conversion (seen at the backside of the cilinderhead/in front of the inlet manifold and the bottle at the side of the radiator/behind the left head light), both (airco + LPG conversion) are for now not important)

With these pictures you can see the first seen optical differences when the hood is being openend.

 

Donor car is a 1996, mine 1995

 

Because my English isn't that well, better said terrible, perhaps horrible, i eventualy went to: https://en.wikipedia.org/wiki/Saab_H_engine#B204_and_B234 and i know, there are a lot of people who says "That website isn't always that good!", but, for some basic information for now it should bee good enough and on that website you can see that the biggest difference by these later engines for the SAAB 9000, the B204x and the B234x, has to be found in a different stroke.
The B204x engine has a stroke of 78mm, while the B234x engine has a stroke of 90mm and that by the identical bore of 90mm.
Different stroke in the same engine block, means different crank shaft and other connecting rods.
You found out that the pistons are different to and that surprises me not because the connecting rods makes different movements in the B204x engines as those in the B234x engines.

What i for now not know, but you have a donor car and for now i give you one other point what could be different between the B20x engines and the B234x engines, is the fuel pressure at the fuel rail/fuel injectors, that and more information have to be found out.

 

Ooooooooooooopppppppppppsssssssssssssss!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I thought we were talking about a NA aspirated B204i and a NA aspirated B234i, but we are talking about the use of engine parts from a NA B204i into a turbo charged B234L!
Sh*t, i'm gonna be old!

There is only ONE TIP i could give: STOP WITH THIS CONVERSION!
The compression ratio is different and a lot more details and components are completely different and stay with the pistons, they have a different shape, think about the different compression ratio, while the engine blocks and cilinder heads are identical, then the pistons have indeed a different shape and those in the turbo charged B234L have cooling by oil what is sprayed to the down side of the pistons.
Then all the different other parts, this conversion will be going to be a nightmare with a lot of extra jobs.

The best conclussion would be: Buy another B234L engine or if you would have a 2 liter version, buy a B204L engine and this last one exists, but i difficult to find because was limited for some markets, mostly Italy and Greece and was used in those countries in the Aero and the Griffin versions, due to the Tax regluations in those countries.
So the B234L engine is difficult to find in Poland, the B204L even more difficult, but, then there is another soultion: Buy a B204E engine (=Low Pressure Turbo version, orignal from factory 150hp) and then tuned to the specifiactions of the B204L 185hp engine.
In the situation you wil use a tuned B204E engine, you will need the remaped ECU for the 185hp B204L engine, found left in the bay in the engine room, below the front window, let's say where the window wiper mecanism is found.

 

Thanks for your input, appreciate it.
It took a long time but I just got my crankshaft repaired and hopefully its gonna work and last.
We'll see.
Cheers