As a former owner of a 342 (stock bore) in an SN95 here is my .02 cents.
The heavier sn95 needs the extra low end torque of the 342 for sure. However there are a few drawbacks to the SN95.
First the SN95 computer will need a chip burnt for it or some other type of tuning help. The reason is the load base nature of the sn95 EEC units. Because the 347 will take in aprox. 13% more air than the 302 its programed for the EEC will think the engine is under more load than it is and put in more timing. Until I figured this out I constantly had pinging problems.
Second the elbow setup of an sn95 cuts back on the intakes flow over a fox setup. This will make it harder to pull in the upper rpms.
The biggest problem most people have (myself included) is a 347 needs a larger intake and head than a 306 period. I was running a GT40 and Edelbrock performer heads and it was all done in by 5500. While I never had it dynoed Rick Anderson told me that my combo probably peaked around 4500-4800 rpm, which I believe from driving it.
If I was to do it again I would say AFR185s and a Holly system max are the smallest parts to go with a 347 if you want to play in upper rpms.
You can still have a lot of fun as a daily driver with "smaller" parts, but it just won;t pull the rpms.
My 95 with an AODE, 2800pi converter, 3.27 gears ran 12.80s just leaving it in drive and letting it shift itself around 5000 rpm.
So it all comes down to what you want, but I'd go woth more cubes in the heavy sn95 for sure. You'll just need to get the right top half to make it do what you want it to.