[C10 - C90 Bill]

I checked in one of my 70-80 Chevy Manuals and although my book is dated '67 the HM-80 states the standard engine is a 401M and the optional a 478M. If it's the original engine still in there, it looks like it will be a Magnum. I always figured the 70 had the 401 and the 80 a 478, but let us know which one if you buy it.