Yes, that's a cheap poppet style thermostat. Summit shows the sleeve style as a "high performance" thermostat. But the local auto parts house will have them also, the last one I bought cost about 8 bucks I think..

I also agree with Mike P., ditch that fan and get a 6 or 7 blade Ford fan and get it as close to 1/2 into the shroud to stop recirculation of the same air.

And lastly, get the timing sorted out. You might be close but how can you know?? Small Chevy's have all the timing parts easily available and cheap enough that there's no real excuse to be guessing. This can affect your temperatures and your cranking to boot.