1900's +ohio lookup (please)

I am searching for anything on my paternal grandparents, & even though I still have aunts & uncles the grandparents kept their mouths closed about things, & no one can even give me their correct last names!

I do know they were buried under the name of "Pawlak" my grandmother died in the 1960's. (I have seen their gravestones - holy cross cemetery , cleveland oh)( I was born in 1953, & don't even remember IF I ever met my grandfather.)

my fathers death certificate (Charles Pavlac b.10/10/23 cleveland Oh - d.7/20/78 cleveland Oh) lists parents as :John Pavlac & Helen Zalenka.(that info was given to the coroners office by my brother, & I don't know where he got it, & he also is now deceased).My father had brothers named George, Andrew ,John & sister Helen + others( about 8 kids). My dad told me (when I was a kid) that his parents name when they came to the US from Czechoslovakia was "pavlokowski"( spelling I am not sure of). my dads brothers have different last names, also, with a couple going with "Pavlik" my dad took "Pavlac"( & I dunno why).
Please if you can help*a big * thank you, as I am totally stuck!!!!