The stock listed for the 1100 model cannot be used as a substitute for the model 48. There is a difference in frame size and inletting.
The forend specified is a replacement and it does not have an original Remington style insert. It does have a Remington style steel ring at the front and a replacement steel reinforcing bracket at the rear, in place of the original style insert.
Item number 96980 REMINGTON 1148 Friction Piece, 12 GA. is the standard flat spring style friction piece (about 3/4" wide) used on most models. Item number 1161090 REMINGTON 1148, SPT 48 Friction Ring, 12 Ga. is the ring used to adjust for heavy or light loads for 11-48 models with a serial number range of 5,000,001 to 5,026,000 and for SPT 48 models with a serial number of 3,000,001 to 3,027,000. This friction ring is thicker than the friction piece and it is beveled on the inside edges and it is about 1/2" wide.
Item number 1152830B REMINGTON 1100 Magazine Cap w/ Swivel Assembly Hole, Police, 12 Ga., Matte Blued, New will fit the 11-48 model, however the swivel assembly is not available. If you are looking for a cap and swivel assembly that can be used as a substitute for your model you may want to see item number 779570 REMINGTON 870 Magazine Cap, 12, 16 & 20 GA., Blue, W/ Swivel or item number 826000 REMINGTON 870 Magazine Cap, 12 GA., Parkerized, W/ Swivel.