Hi Flash....
If you mean the installation pattern (mounting bolts) the SJ-40 through SJ-60L match the OS46FX pattern (and assorted clones). Drive washer spacing is very close too. Pretty much drops in place where an OS46 goes (just the carb is a bit bigger and at a different angle)
The muffler bolt pattern matches an ST-40
Dimensions are on the web site
http://www.jettengineering.com/tech/dimensions.html
Bob