Helicoil or tap for larger bolt??

[53burb]

First off, this is on a '55 Chevy Bel Air with an early 70s 350 I'm putting in it. As has happened many times to others, after changing the thermostat, the passenger side bolt hole on the water outlet stripped. This is the original cast iron intake. The bolt hole is so worn that the 3/8" bolt will just drop in for the most part. Do you think its easier to use a helicoil or retap it for a 7/16th bolt? I have an Harbor Freight tap and die set that I used on a riding lawnmower engine years ago. Thats the real only experience I have with it. Never have helicoiled anything. Thoughts?

https://www.amazon.com/Helicoil-5521...83463582&psc=1