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I didn't put the tabs in when I did a coolant flush a couple of years ago based on that Tech Bulletin. I did replace the upper and lower radiator hoses at the time and even reused the original sping clamps. No leaks anywhere so far.
I figured that the tabs that were put in originally helped to seal any leaks especially around gaskets. If this material flows around the gaskets and maiting surfaces and then seals, it should last assuming that you don't use any sort of chemical flush when changing coolant.
If I had a problem with porosity in the aluminum heads or a leak I would use what the factory uses - Bars Leak. I had used this product when I first got my 85 and there was an intake coolant leak. After using Bars Leak the leak was sealed for the 12 years I owned the car. I think it is a great product - just shake it well before you use it.
Though I would recommend that you add the pellets/BarsLeak through the radiator hose and not the surge tank. GM recommends the lower hose but I've had no difficulty adding it through the top hose.
I believe the aim is to have the material in the radiator.
The surge/expansion tank, while part of the pressurized system, is not in the flow. Rather it is located at the highest point in the system, above the engine and plumbed with smaller hoses to allow the escape of air (cavitation) produced by pump activity.
There is a great deal of info about this at Cadillacforums.com. The site is very similar to this one and just as easy to navigate. Do a search and you will find a great deal of info.