Stop in for a cup of coffee

Rainy Day Auto said
It is a small block.

Try it and I bet you it is. I don't think there is a centered top hole, I am 99.999% sure that IS a small block 727

Well now I have to run back out there. My 340 has a top centered hole...and it does for sure. Hmmmmm

But, you are right!!! Just dug out my 727 transmission handbook and it matches for a small block.