the 289 block and the 302 block are the same. the only distinguishing factor is the 289 block is stamped 289. thats it. it is the stroke that determines the size between these two. you can build a 302 with a 289 block and visa versa.

why someone wuold switch the heads from a 302 with 289 is beyond me but people do things all sorts of different ways. therefore i would not guage anything about what is in a block by what the heads say.

But im not sure what the HP diff. ws from the 289 to the 302. anyone know?

 

Like I said, some 302 parts were used when the factories started running out of 289 parts in '68. It's not uncommon to have a 289 motor built with a 302 block and heads. At that point, unless you're absolutely certain it's the original motor, the only sure way to tell which crank is in it is to measure the stroke. Checking the block casting number or looking at the stampings on the heads will not tell you for sure, unless they're 289 stampings.