Holley Pro-Jection for a 258?

[Tom Jennings <tomj@xxxxxxx>]

I tried calling Holley, but they don't seem to have application
support...

I may get rid of my tax return with a Holley Pro-Ject system for
my Hornet. (No LP conversion at this time; I want on-road fast!)

Holley makes one kit, 501-12, that is a 300cfm bolt-on for the
Jeep 258. This sounds like the correct kit for me. However at
least one person is saying I should get the 670 CFM kit instead.
There's no real difference in price, and both are 2-bbl replacements.

Will the 670 work OK at low speeds/low CFM?

Does this sound right? Are holley CFM ratings conservative or
bragging?

I'm looking for a used one, if anyone has one, digital only.