340 TA Heads....

Not sure how the Port-O-Sonic compared to the others when using a Holley carb, but it was suppose to be better than the LD340 in Super Stock when the "popsicle stick" mod was used to help fuel distribution with a Thermoquad. The Holley Strip Dominator superseded that when it was introduced.

While it's not a "backyard" project, machining the original pushrod holes to allow a press-fit of a metal slug and redrilling them to the T/A location was the usual procedure. Using a metal slug that was a different color/shade would help you see where you were in the porting process.