I have 3 SM's on LP. Two are factory and one is a conversion. All have an "East/West" tank. This one is a conversion.
On Craigslist in this area it would bring around $1500. You might could get more if you hold out for someone that knows what the grill is worth.
What are the suffixes on the tag? I have a SMTA,LP cotton picker. Has the same axle housings. The tag suffixes will tell if it came with those or if someone put some pieces together. I'm curious if this is a late or early SM. The one I have that's a conversion is a stage II but has the belly hydraulics.
Motor should be nice and clean inside having been on Lp.