^ repowered with complete long block, not sure p/n but was a stock GM reman with national warranty..
new heads are 862 which I believe are very similar to 706
this was a widely known issue, google this TSB, there's chat on lots of forums about it..
#06-06-01-019B
I was guesstimating my timeline above, engine swap was July 2015 157k miles..
probably drinking coolant since 2013 or so.. water pump was replaced in 2014 for very minor leak while at my buddy's garage for other work..
I was 99% sure the tiny little dribble not reaching the ground wasn't the cause of the volume of coolant it was losing..
but had him replace the water pump anyway with high hopes it wasn't the heads..
less than a month later the factory new GM water pump was leaking, tube fitting to cast b/o, ended up replacing that one myself
year later it was up to a gallon a week or more.. at the end, stopped three times to refill expansion tank getting it to Henderson for repower..
problem with being a professional mechanic for a company where you can't work on your own vehicles..
often have to rely on other garages and friends to handle jobs you don't have time for in your driveway..
timing always seems to be lousy for breakdowns.. knock sensors, fuel pump etc. I did because they went b/o when I had time..
good luck!