What condition is everything in? Is the carb new'ish or could it stand to be rebuilt? Also, how well adjusted is it for running in a mile-high city? That elevation affects performance. You may need to optimize your air-fuel mixture.

Getting everything you already have working up to its potential by tuning up might be in order? Dialing in more distributor advance often works wonders.

You could modernize by swapping in a Magnum Engine, but you'll need to make other changes as well. Maybe a nice old-school 360 and re-using some of your existing parts might work? Swap on some headers and add a Sure-Grip.