[ox_ford_guy]

Bill.....I had a similar problem. Those rubber blanking caps are not reinforced and cannot take higher heat and pressures.

As long as the curved hose is in place (thermostat bypass hose) I agree that tapping out the pump is likely your best solution.

However, another approach is possible:

On my Cobra, I clamped a 3" long piece of reinforced heater hose on the heater fitting with a male pipe fitting (with flanged hose clamping area) and pipe threads on the end. I then plugged the pipe thread end with a female cast iron pipe cap.
Got the pieces at NAPA and home depot.

Is mostly hidden by the pump on my 351w, looks fine and has worked out well so far.

Good luck...ox_ford_guy