Howdy, Wendol
Been looking into this myself. The Cat 1 ball socket on the back of your L3800 fits a 7/8 inch diameter pin. The hooks on the quick hitches vary all over the place as to the pin diameter they "fit". Depending on the specific quick hitch, it may take a bushing to go from a cat 1 to a cat 2 diameter to get the pin to firmly set in the hook.
The bushings with the large end and roll pin will likely not work due to the individual implements. Every one of my six implements has a different spacing.
Also with a land pride mower attached to a fixed quick change you will lose the articulation of the mower as you go over hills and cross gullies and rills.
Another choice is to look at Pat's Easy Quick Change. This allows you to match the spacing for any of your implements and to keep articulation for your mower.
As far as the fixed quick hitches, Land Pride QH15 27" inside, 29-1/2" outside; Northern Tool 26-1/2" inside, 28-3/4" outside; AgriSupply 27-1/4" center to center; Harbor Freight 27-3/16" clearance. None of these will fit my disc (Cat 1). Northern Tool will not fit my Land Pride mower.