you can (in all 737 variants I have worked on ) pull the spd brk lever fully aft past the flt splr mark.None I am familiar with have a physical detent.
But you will only get flt splrs regardless of handle position.
You need (as per previous post) w on w (rh gear) and wheel spin up (60 knots I think it is and or reverse selected in certain conditions) to get the actual splr panels past the flt position.
So , from memory, you'd need a few failures to get gnd splrs in the air (never seen it thankfully)
You can physically select gnd splrs but it wont go there in a normal serviceable aircraft in flt.