Old Fard-No
Gjanes- +1 to Progressive/Traxxion (OEM Inadequate/Inferior post-Trike).
"Some",,,, differ.
Also, there are differing Lengths (as DonFor said), Spring-Rates, Spacers or No Spacers (and differing lengths of those), and Fork Oil viscosity and amount, Triple Tree modified then Fork Extensions yes or no (hopefully Yes),,, ALL which will affect the equation and experience of Progressive, Traxxion or any Spring for that matter. Like a good Chilli, you have to dial in ALL the ingredients to get it "right".
Don't get all caught up in the after-market (non-standard OEM) Spring YES or NO. It IS a YES when converting to a Trike.
The Real question of Which/What/How will vary by Brand Kit and which Bike and then the proper corresponding variables (listed above) to fit appropriately. WHOLE lot to consider to get a truly Accurate & Complete Picture/Answer. The Front-End of any Trike is an Assembly. It has to be thought of and addressed as such. To be correct anyways... Can't just flippantly throw pieces at the wall and when they don't "stick" toss them away. Not the Piece that's wrong-It's the Application/Applier that's to blame.
In Trikes, there really are some YES or NO's that are simply NOT, YES or NO ThumbUp