If the carbs do NOT have screw-on float bowls, they are for the 1970-1976 "K" model bikes. These come in 4 basic models, identified by the little number stamped on the front top of the carb body:
7A - found on 1970 K1 and 1975 F0 bikes. The early ones have "A" calibration, with brass floats, 24mm float depth, 115 mainjet with needle clip in 4th notch from the top, or else 120 mainjet with clip in middle notch. The airscrews on teh early ones have a tiny hole in their tip, while the ones from the "F" bikes do not. Most (but not all) of the F0 bikes had plastic floats and 26mm float depth.
657A - found on later K1 and early K2 bikes. These have 110 mainjets with the clip in the 4th position from top, and tiny holes in the air screw tip. The float level is 25mm, measured from a small pedestal on the INSIDE of the gasket. (Same as 7A, BTW). These carbs will idle well at 850-950 RPM.
657B - found on K2 and later bikes, through K5. These usually have 105 mainjets, needle clip in 4th notch from top, floats at 26mm, air screw tips are solid. These carbs complement the Hitachi spark advancers with reduced advance angle, and idle around 1100 RPM, all have plastic floats. The float depth is measured from the notch in the outside edge of the float gasket area, is set to 26mm.
087A - found on some K5/K6 and F1 bikes: calibration is similar to 657B carbs. The idle air screw shape is different (to allow for a plastic cap to prevent you from adjusting it, probably now long gone from heating), choke lever on the opposite side from previous carbs, single hose feeds fuel to whole rack from the 1-outlet petcock on tank.
The PD carbs came in PD41 and PD42. The main difference seems to be the non-removable idle jet in the PD42, probably to make the EPA happy. Most of these have 105 mainjets and after 1977, non-adjustable needles.
