The engines I started with is actualy the 6J2 because you need evenly spaced bores.
I think these heads can also be adapted to the other uneven Simca engines but I didn't try. If yes I'd try with the shortest stroke.
I have to admit having 5 of these 1590 cc engines versus only 4 1440, one 1290, and one 1200 cc.
In order to rebore a worn 1590 engine, you need to be either very lucky
and have a set of large overbore pistons, to use pistons comming from another make of engines or rob your bank and go for custom built forged pistons.
This will mean an engine of about 1700 cc.
Given that the original VW of 1800 cc was producing about 140 BHP (din), an easy calculation would leave something close to 130 BHP for an engine having the same type of injection.
Replace the injection by 2 horizontal carbs and ... I can only expect at least a similar number
Replace the cams by a schrick and it's said to produce 25 extra bhp, so about 155
Add a compressor ... I don't know
But I've seen such an engine, based on the 1290 cc, without blower, delivering 160 bhp, like nothing.
Actually, I would first be happy that it'd work ...
I'm not speaking about an intercooler but a charge cooler which may need less room in the engine bay but will mean other issues for the cold water supply ...