I didn't notch the rear of my most recent '66, just trimmed the bump stops to keep the axle off the frame at full compression. At this height it has about 1.5" of travel before it hits the bump stops. Currently it has relocated shocks so they're more effective, and the shocks are valved a bit too stiff which usually keeps it from bottoming out on the bump stops. It has 1.5" drop blocks and D2600 air bags on schrader valves so I can adjust the height and lift it back up when hauling a lot of weight. With softer shocks or lower height you'd need a notch.
My old '66 had the same rear shock relocation but with softer valved shocks, a 2.5" pipe notch, 2" drop blocks, and unknown drop springs. It sat roughly 1" lower all around than the current truck. It rode great with the softer shocks and extra travel from the notch.
I would do a small weld in pipe notch over the usual bolt in c-notch kits, the c-notch kits cut away an unnecessary amount of frame for the amount of travel gained- the diff housing will hit the bed before you use up all the travel that a bolt in notch has. If you plan on towing or hauling weight behind the axle a weld in pipe notch with the frame boxed will be much stronger than a bolt in style notch.
Both trucks have 215/75 front tires on stock wheels with 1.5" bolt on spacers to clear the calipers and push the wheels out closer to the fender lip to fill up the fenderwell better, and 235/75 rear tires on old 8" chrome reverse aftermarket wheels that have 3.25" backspacing.
