Holley square bore adaptor

“If” the throttle blades on a SA670 interfere(or some other part of the linkage) with the stock square flange 340 manifold(I would test fit it with no gasket), then you need a simple spacer, not an adapter.
Something like a 1/2” 4 hole unit should take care of it.

Allstar Performance ALL25983 Allstar Performance Drag Hi-Flow Carburetor Spacers | Summit Racing

(Actually, the steel Ede plate you already have may be enough to take care of it, if there is an issue)