I have been in the same situation. I can confirm that AC Delco #18M1036 is the deep bore that you will need with your setup. Also GM #19176594.
See my thread link (with photos) regarding similar issue and question regarding if the deep bore/long push rod in booster was correct. On my 72 Blazer it was that way from factory. Details here:
https://67-72chevytrucks.com/vboard/...d.php?t=845821