The RIPS alignment feature began when the NM Flattop and New Vaquero were introduced.
They were not and will not be added to any pre existing models unless there is sufficient reason to modify their production programming; too costly to change.
Reverse Indexing Pawl System (RIPS): All the NM FT Blackhawks and NEW Vaqs have this system which allows the cyl to roll backwards enough and stop for the chambers to align to the loading gate trough without the hammer on half cock (which can't be done on standard new models). You can see the device (3 parts) in the hammer channel to the lower left of the cyl pin hole shown below. Grip frames from models w/o this system need a divot cut above the trigger guard for the free spin cyl pawl.
Ruger free spin pawl on the right:
Divot for free spin pawl on NM Flat Tops and New Vaqueros with the reverse indexing pawl system shown on the left:
Cutting the divot: To locate this notch, take a measurement from the location on your original GF. Or mark that area on the replacement GF with a magic marker, assemble the GF to the gun, then cock the hammer a few times. This will leave a 'witness' mark in the marker ink, so you simply make the "divot" there. Be cautious not to let the cut extend to the outside edge of the grip frame or it will show when assembled, and don't cut notch too deep!
Use a thin cut-off blade in a Dremel tool. With grip frame in a vice, and your old grip frame nearby for reference, hold the Dremel with two hands for control. And replicate the divot in the new grip frame. It's easier to clamp the Dremel tool in the vice at an angle and hold the grip frame instead.
"Reverse Indexing Pawl System" names of parts, Ruger Part #s & Brownell Part #s (about $15 total):
Cylinder Rotation Stop Screw KMVQ04501 780-001-294ah
Ejector Alignment Pawl (not to be confused with the Cyl pawl) KMVQ04502 780-001-292ah
Cylinder rotation Stop Spring KMVQ04500 780-001-293ah
Cyl free spin pawl (must be shortened for single six frame size) KMVQ00701 780-001-296WB
Or just modify your pawl to a free wheel cylinder pawl. No cost and almost no skill required, and won'y have to cut a divot in grip frame if your new grip frame doesn't have one:
http://marauder.homestead.com/files/FreeSpin.html