RE: 804stroke same as 704s
In the ASP/Magnum engines, the 65 thru 91 are in the same case.
But, around 2000 they changed the mounting hole spacing from that of a Saito to that of OS engines. So your 80 may have the short bolt hole spacing front to rear but the dimension left to right is the same on both versions. It is the same requirement between the mounting beams on both versions.
Enjoy,
Jim