Just sharing my similar experience, and results:

I have a 4 bolt 350 in a 56 convertible. It was stock bore, but with a B&M 144 blower. I used the original radiator on it for 15 years, and no heating problems.

I rebuilt it in 1999, and due to a head gasket failure a few years earlier, I had pitted cylindars. I bored it 30; I also changed the cam to one 'designed' to work with the blower. And, I put a new alumin, larger, Walker radiator in the car. (I only did that to get the polished aluminum look.)

After all that, this engine had heating problems.

I finally fixed it with: Aluminum flex fan on motor AND high RPM Spal elec fan on front of radiator (on all the time). I also put on a high volume water pump. Oh, and a fan shroud.

Engine runs very cool now. I tried early this summer to have the electric fan off (I'd like to take it off...for looks). But I found I need that fan running too.

I'm presuming my heat problem was more due to the bore than the cam...but who knows?