1. Nitrous Express makes a quality product. Their single nozzle systems make good power and are easy to install:
www.nitrousexpress.com
2. I wouldn't go past 150hp with the stock bottom-end.
3. The single most important add-on you could install w/ your nitrous system (esp. for stick cars) is an
RPM window switch. It's not absolutely necessary, but it should be considered.
Also, I'd recommend a bottle heater and nitrous pressure gauge... you MUST have a minimum of 900-1000psi in order for the system to be optimized.
Other goodies you'll want/need.... purge valve, fuel press. safety switch, fuel press. gauge (that can be monitored from the driver's seat). Oh, and a colder set of spark plugs gapped @ .035"
-Ryan