An idea for you, if this is the direction that you're thinking about:
On my Olds, I ran a "center feed" cooling set-up for several years: I removed the center freeze plugs on each side of the block, and made some inserts that allow me to feed water into the center freeze plug location on each side of the block. I tapped all four corners of the intake manifold for water outlet fittings, and tee'd the pairs together on each side (left, right), feeding two thru-transoms out the back, above the water line
