I think that if you just want to lower it slightly and not have to do much work you may want to consider 2 1/2 inch drop spindles in the front and than drop springs in the rear. If you still want something of a slight rake in the stance than 3 in rear springs will work. If you want to get level more like 4 in drop springs. But if you drop to 4 in you will have to change the shock mounts and add an adjustable track arm.
I prefer Drop spindles because it maintains the front suspension geometry. In my experience in these trucks and also in a 56 Bel Air if you use drop springs the vehicles ride will be choppy. Also using spindles makes it easy to add disk brakes if you have not already done so.
Also do you have sway bars? A sway bar in the front makes a big difference on these trucks. If you only lower 2 to 3 in nothing needs to be changed with the sway bar mounts, but if you lowered the front end more than that you will need to change the mounting brackets. Rear sway bars do help with handling but not as much as what I have seen on cars.
A decent set of shocks always make a difference. If you go a lot lower than stock you need different shocks that are shorter.
Early Classic has really good parts for this and a very helpful staff. I have worked with them a few times for parts for my truck and for a few friends trucks.
http://www.earlyclassic.com/catalog.aspx?ProductId=261