That site is so full of mistakes it is hardly worth reading. It is correct that this is a truck head, though.https://www.ramscyl.com/headcastingnumbers.pdf
3788555
CHEVROLET C + K SERIES TRUCKS
58-65
5.7
348
V8
This is one Man you should listen to Don has been around and knows his $hit and is willing to offer help.Everything is an anchor to you