yea, I certainly wouldn't get rid of vacuum advance, your highway mileage will suck, your plugs will carbon up fast, etc.
You just need to dial in the right timing curve. I'd recommend an MSD 960001 or whatever it is, the fully adjustable vacuum can. You can limit your max vacuum advance, change what vacuum level it comes in on, and that kit comes with mechanical advance springs, to choose when that starts coming in, and when it finishes.
You may want to hook up your vacuum advance to manifold vacuum, that'll give you more advance at idle. Or you can use ported, and bump up your base timing, then weld your mechanical advance slot shorter. (IMHO manifold vacuum is easier
) however you may end up with your manifold vacuum giving you a hunting idle, kinda depends on the motor. Best bet is to try a few combinations and see what works best for you.
that timing (18 base, 36 total) is probably a good starting point. I think stock mechanical is around 20* travel. Lots of different ways to skin the cat here.
oh right, and say you went 18* initial (that's mostly a guess and check thing), then 36* "total" (that's pretty much the same for most SBC motors.), then you could use around 52* at cruise. Yes, that's right 50* degrees of timing at cruise. If you had that much at WOT you'd ping, but at light loads like cruising, it's ok. Hence, vacuum advance.