As for the b16 tranny...per my gps it tops out at 117mph with my b20 (nonvtec) and my limiter raised to 7200rpm. With a gsr motor you should see around 120-125mph top speed.

The block idea sounds fun but you will be in a non cost effective boat. If your going that direction then I am sorry I would have to say turbo only.

I would do the LHT deal. The nitrous will work but it will get annoying having to refill it all the time.

Meth kits work great from what I hear on turbo setups but I have never used one myself.

Get the LHT aftercooler thing and install it yourself and have someone else tune it. Problem solved about converting to s300.