If you have any kind of cam you will need about a "3000 rpm" converter to be streetable even with the blower. remember the blower isn't doing anything except mix the air fuel at idle and not much more just cruising. You can have very high vac at cruise.
Now, just asking for a 3000 converter will get you something rated for NA motors, and relatively inexpensive. However a 6-71 sbc will make huge torque at 2000 rpm and even lower so this converter will "flash" or stall much higher. This is why the guys are recommending high performance and well built units. The lower priced ones will eventually fail due to over loading.
I have a 3000 NA converter that flashes to 4000 plus without trying very hard. Needless to say I don't abuse it very often. Nothing like having a major problem 50 miles into nowhere back roads when out crusing with the guys. Even with AAA and extended coverage it still is an all day experience getting towed home.
My car is very light at 2800 lbs rolling so the drive line isn't loaded like your truck will be.
Get a good one....a failed converter will probably take the trans with it.
This rating works very well on the street and is very comfortable to drive. Even crusing at highway speeds it does not slip much. I use a medium sized trans cooler and seldom see temps over 150-180.