My 64 300 had those hold downs, the engine was stamped with a T then over stamped with a V. I think those head casting numbers, 4 bolt valve cover, rocker stands, ended in 3200?

I couldn't get the aluminum stands off the steel shafts so my solution was to get a set of NOS 906 heads from Len Dawson, this was in the late 80's when you could still get them.