There isnt a straight formula that tells you how much power you will get for a bar of boost.

On one hand you probably only have about 13 psi absolute in your manifold currenly (due to intake restrictions) so 29psi from a bar of boost is way more than double, so it looks like you should get more than 100% gains, but then you have to take into account the change in intake temps, which bring it back down, especially if non intercooled.
If you then consider the exhaust side as well, you have to consider what bolting two quite restrictive snails on would do to your N/A power output in the first place.

All that said, I'd expect 5psi to give you roughly the sort of gains you are looking for and some really good torque increases as well, but I would want to put it on mappable ignition at least, and preferably management for the fuelling too, as to get the best from a high cr turbo conversion you do need to be careful about how its mapped, and on a carb and dizzy its hard to get right (although possible of course)

If you can add an intercooler, it would really be worthwhile doing so, even on low boost.