I'm going back to circulator pump.

First installed cross over, non-thermostat version in 2003 without stats, I found that I did not run long enough at WOT to get heat into engine or oil.
Changed to crossover with bypass that has the 1/2 inch hose and three hole drillled thermo. This works OK.
Upgraded to crossover with 3/4" - 1" hose for better oil cooler flow when thermo closed, not enough water pressure to force water through blocks at idle speed, with 120 degree thermo engine temps to 200+ unless I dropped out of gear and boosted rpm for a while.
When back to 1/2 inch bypass hose version, but these really restrict water flow through oil cooler at low rpm cruise, but engine temps stay at thermo temp.

The beauty of the Circulator pump is that at all times the coolers and exhausts sees wide open flow, and the engine gets water flow it needs separately so it does not matter if flow is a trickle if that is all it needs.

So, I'll be listing all three sets soon to finance the SS thermo housing and circulator pumps with v-belt pulley.