The factory dust cover should fit normally with Bob's Knobs installed. If your dust cover contacts the knobs, the manufacturer will provide a set of spacers that attach to the inside of the dust cover to move it slightly away from the secondary assembly. You can also press the center of the cover from the inside to contour it for additional clearance.
Pre-2005 Meade 8 inch (20 cm) telescopes have three screws on the secondary housing and no fourth screw on the side. The surface of the 3-screw secondary is textured, not smooth like the surface of the 4-screw secondary. The 3-screw secondary requires different knobs. Do not use knobs for the 4-screw secondary on the 3-screw secondary. The screws on the 4-screw knobs are too long.
An Allen wrench for removing the factory collimation screws is included with your order.