imco boxes
 

looking for a pair of -1 or -1 imco extension boxes

I think Imco boxes are up 3" and the engines need to be raised.Stellings boxes are adjustable from what they call neutral "0" to up 3" but they go on to say that their "0' position is actually up 7/8". I would say look for stellings and run the "0" position with their shaft kit the engines don't need to me moved. I have a set of their shafts that I didn't use since we moved my engines forward 2' if you find a set of boxes and no shafts. I might be wrong on the Imco boxes but just my 2ct's.

You are correct fire....Imco has a Neutral box and a -3 Raised Box which you have to raise the engine up 3".

Best setup would be to get the Neutral Box and see if you raised at all they build in a 13 degree angle into the box depending on your transom angle you could gain or loose...I gained a inch when I put them on then added -2 Imco lowers so raised my prop height up 3" which works great with my setup.