Hi,
Vans does sell a rear throttle kit that includes a side plate. Now that you already have the quadrant, you may be able to buy just the side plate. The drawing for the rear throttle installation is OP-2. You can probably get the drawing and the side plate separately. Might even be able to get the drawing on line? The part number for the side plate is F-8114A.
Note that the F-860B-L fuselage rib gets slotted for the throttle lever, so that the quadrant doesn't extend into the cabin -- the whole thing fits in the space between the outer skin and the side plate that fits onto the F-805 and F-806 bulkheads and the F-860B-L rib. I used a small abrasive wheel in a Dremel tool to cut the slot. A angle die grinder with an abrasive wheel would work too.
Reaching into the cavity above the F-860B-L rib to operate the throttle is quite comfortable. I think the lever is bent inward some just above where it comes out of the slot to help move the knob inboard away from the outer skin some, for more hand room.
DO NOT cut a big square cutout in the F-860B-L rib to accept the whole quadrant. Cut a slot big enough for the lever only. You hopefully can assemble the quadrant around this slot so that the nice labeled top plate can sit on top of the F-860B-L. If not, it will be hidden underneath. Too bad, but don't cripple the fuselage structure by notching the F-860.
You need to make holes in the F-805 bulkhead and the two F-804 fore and aft bulkheads for the pushrod that links the rear throttle to the fwd throttle.
I used a Unibit stepped bit for this, works great.
You can start with a small hole, pull a string between the front and rear throttle lever connections and see where you need to move the hole. Drill another small hole and check again. Once you have the location right, open up the hole diameter to allow the link rod to move without rubbing. This larger hole will engulf your smaller trial hole(s).
By mounting the quadrant recessed into the fuselage space, it allows the holes in the bulkheads for the link rod to be near the middle of the width of the bulkheads.
DO NOT notch the bulkheads through the flanges on the inboard edges of the bulkheads.
Be advised: On the older kits, the plans indicated the hole location for the throttle link rod, and also indicate a location for the manual elevator trim cable.
These are on different drawings and they conflict. 
So if you have manual elevator trim cable, you have to relocate the hole through the F804 bulkhead. Unfortunately, I had already drilled the hole for the trim cable, and the combination of that hole overlapping the throttle link rod hole left a pretty big hole in the F-804, so I riveted doublers on the insides of the fore and aft F-804 bulkheads for some distance around, above, and below the holes. PITA!
I believe on the later matched-hole, -01 kits (after mid 2007), they fixed this and I think some of the bulkheads may already have the holes in them. Perhaps not the F-804 though, I don't know. So proceed forewarned to keep the manual trim cable and the throttle link separated by a few inches.