Might work. Hoping to find the SH600.What about a touring frame? Geometry wouldn't be much different. Depending on what the drivetrain is, it might only require a bar/stem/shifter change to convert.
Have a look at the 1990 catalog. Geometry for the 25" SH and ST frames is exactly the same. The only difference is that the SH fork has a bit less rake which results in more trail. I doubt you would notice the difference. Do you need cantilever brakes? Some of the older touring bikes used mid reach calipers. They will still take a 35 mm tire, maybe a bit more. I have a mid 80s ST500 that I could probably sell. Think it's a 25", will check.
Hi, I have a 1990 SH600 2+2 serial number is 02101907720 looking to sell, was a great bike. Cleaning basement prior to moving. email direct at hattertown@aol.com if interested, would be nice to get it a great home. Joe