Original M1887's were made with both Damascus and fluid steel barrels. I would NOT, UNDER ANY CIRCUMSTANCES shoot one with a Damascus barrel, due to the possibility of intergrannular corrosion along the seam boundaries of the welded strips of iron. With fluid steel barrels, it is possible to shoot BP or LIGHT smokeless loads, IF THE GUN HAS BEEN THOROUGHLY CHECKED OUT BY A GUNSMITH FAMILIAR WITH THE Model '87. As to shell length, there is no question that the chambers of the original '87's were intended for 2-9/16" shells. If the fluid steel barrel has enough "meat" on it, the chambers should be lengthened to 2-3/4" and a LONG FORCING CONE cut. Modern star-crimped shotshells with plastic shot columns would be constricted in the original short chambers, causing pressures to rise DANGEROUSLY! The long forcing cone, combined with the lengthened chamber will spread the pressure-time curve. Nonetheless, it is VITAL to use Low-Noise, Low-Recoil or similar shells.
Frankly, although I have fired original '87's, and think they are "neat", given the limitation of two shells loaded at a time, on, say, a six-round course of fire, requiring loading of two shells at a time, they are certainly not the choice for SASS competition. IMHO, the repro '87's with the "load-two" modifcation is a better choice, if one desires to use an '87 for SASS matches. I guess it depends on how "reasonably" you can acquire the arm, and the cost of inspection and modification. In addition, the original guns are probably less durable due to the vintage steel of which they are made.
Hope this is of some help.
Happy New Year, Pard!