The tuning system starts here with a slug tuned coil.

You need two blocks about 1" square and 1-1/2" long. I used plastic. Stack the blocks and drill a hole where the green line is. This hole needs to be sized to match your core material. I'm using a 1/4" brass screw. I drilled the hole and tapped one block. My former is a sink supply line. The line is 3/8". Drill each block about 1/2 way through with a 3/8" drill using the holes you have drilled as a guide. Stand the blocks on end and drill a hole in the center of each block.(where the red rectangles are). These holes will mount the blocks to your chassis. Tap the holes for mounting screws.(I used 1/4" can be whatever you have on hand.) The core needs to be cut to length.(about 4" should do.) I just marked the core about 1" from one end and another mark 2" away. Wind the coil between the two marks. The coil value will vary with the size wire used. I used #26 wire and the 2" length coil tunes around 3 Mhz with a 120pfd capacitor. I mounted a three terminal block on one mounting block to terminate the wires . (this is optional otherwise you need leads long enough to reach your circuit.) Now you put the coil in the blocks and measure the distance between the mounting holes. Drill two holes in your chassis where the coil is to be mounted and lay the coil on the chassis and use two screws to secure it. Screw your core into the mounting block and the coil is done. Next we assemble and mount the tuning diodes. Another way of doing the coil is found here. Tuning a coil with a brass screw

The tuner with pictures