I like the 350 recommendation but I will never go back to a HEI distributor. I put a Progression Ignition HEI style in mine and I will run it from now on in any SBC or BBC build if it uses a carb.
You install it at 10 degrees BTDC and then set up the timing table with your phone via Bluetooth, you can lock the ignition so it won't fire for anti-theft, it's a drop in replacement for the HEI, it has a rev-limiter built in, you can set it up for boost applications, it retards the timing for easy start up, and it has MAP / RPM / Timing Advance gauges you can watch on your phone while your driving or tuning under the hood.
I've checked it with the timing light and it's dead on. It's pretty cool to adjust on the fly while your driving to fine tune. No pulling over to tweak the distributor and then test, lather, rinse, repeat.
Here's a link
https://progressionignition.com/
And check to see what gears you have in the rear end. If you have a horrible ratio it won't matter how good of an engine you build.