Small block intake

Everyone has covered it so it depends on your budget.

*Free flowing exhaust with 2.25 pipes.H pipe if you care.long case dynomax super turbo mufflers give a nice rumble but run what you like.

*Ignition upgrade of some sort and tune the distributor advance.Likely more initial and make sure the vacuum advance works.

* Run whatever 4 bbl intake and carb you prefer.A dual snorkel intake is a plus.Run some ducting to a cooler air source.
I just did a used Performer intake on my truck 360.

*Anything you do beyond that is up to time and money.These mods will support whatever you do later.