You might consider adding power to the brakes without changing to discs. I don't think there's anything wrong with those giant drums, as far as stopping power...lots more friction material in contact. Discs might be lighter and cool faster...good for a race car...and you could add them later, if desired.
You'll like the 327, and the (truck) 5-speed, presumably with overdrive, will be an excellent choice. I'm building a 327 from a '66 wagon...it was 275hp from the factory...probably end up in my '51 3100.
Have fun.
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