OK. So I took the time to revisit this thread.On paper a 2.67 drive ratio is close to 14.5 lbs of peak boost but the 300 six with a big cam and a ported big valve head probably has a better volumetric efficiency than the Eaton 112 at that pressure level so the boost may be less.
Does the supercharger have a bypass valve?
We had a discussion about drive ratios around 2.3 but I forgot that we had talked about using a wastegate to regulate boost.
This being the case the 2.67 drive ratio would be ok if the boost is regulated.
It still would be better overall if you could use a larger pulley on the supercharger and brought the drive ratio down a bit to around 2.5
You would still have to regulate boost if you want to limit the boost to 10 psi.
As far as connecting rods, the stock rods will work fine if they are Magnafluxed and resized with ARP bolts.
I would still use a forged piston but I will leave that up to you.